Dam removal is of growing interest for the management of sediment fluxes within fluvial basins, morphological evolution and ecological restoration of rivers. If dam removal experiments are now quite well documented for small streams located in the upstream parts of river networks, examples of lowland and relatively large rivers are still scarce. In this study we present a dam removal operation carried out on the Vienne River (France) to restore both sediment and biotic continuity. The Vienne River is 363 km in length. On its middle reaches the average slope is equal to 0.0003 m.m-1 and the average annual discharge is 195 m3.s-1 at the gauging station of Nouâtre. The river is characterized by a sinuous single channel of an average width of 150 m. The sediments are mainly made of a siliceous mixture of sands and gravels and were intensively mined between years 1930 and 1995's. In 1920, a 4 m height dam was built just downstream the confluence between the Vienne and Creuse Rivers triggering a total sediment deposition upstream of 900 000 m3 in 75 years. Hence, in 1998, the removal of the dam increased severely the sediment supply delivered to the Vienne River. The objective of this study is to understand and quantify the fluvial processes and morphological evolution on a reach of 50 km of the Vienne associated with the dam remova and the presence of ancient sand pits located along the riverbed. This study is based on field data collected during 7 surveys performed between 1998 and 2013. This large dataset focuses on bed geometry (detailed bathymetrical surveys), sediment grain size, and bedload fluxes measured using isokinetic samplers. It was combined with a 1D numerical model developed to assess flow dynamics and sediment transport capacity before and after dam removal. Results show that dam removal triggered both headward and progressive (near the dam) erosions and that discharges higher than 100 m3.s-1 were sufficient to erode the sandy sediments trapped by the

The purpose of the report is to evaluate the quality of the Ohio River, atmospheric deposition, and corrosion product samples and their relation to corrosion of Lock and Dam 53 on the Ohio River near Paducah, Kentucky. Chemical determinations of river quality, atmospheric deposition, and corrosion product were performed on samples from Dam 53 and compared to similar determinations at Dam 52 (a control site 19 miles upstream) and to historical data from the region, where available. Statistical methods (summaries and applicable hypothesis tests) were used to help identify water-quality characteristics and environmental factors that have some potential for accelerating corrosion processes at Dam 53.

Riparian vegetation is highly diverse and influences habitat of aquatic and terrestrial wildlife. Riparian vegetation dynamics are driven by stream flow regime, and fluxes of sediment and large woody debris, all of which can be altered by riverdamming. Dam removal is often implemented, in part, to help restore degraded riparian vegetation by reversing the alteration of these key drivers. However, increased disturbance and sediment flux associated with transport and exposure of trapped reservoir sediment can complicate a simple return to pre-dam conditions and can favor exotic species. We are studying the effects of dams and their removal on riparian vegetation along the Elwha River in Washington State, where removal of two large dams began in September 2011. To characterize vegetation composition, structure, and diversity prior to dam removal, we sampled 60-150 vegetation plots in 2004, 2005, and 2010 along five cross-valley transects in each of three river reaches: above both dams (upper reach), between the dams (middle reach), and downstream of both dams (lower reach). In summer 2012, we resampled a subset of our plots in the lower and middle reaches to evaluate vegetation and geomorphic change. We also sampled vegetation, topography, and grain size along newly-established transects within the exposed former reservoir behind Elwha Dam, which was removed in 2011 and 2012. Plant community distribution on bottomland geomorphic surfaces along the Elwha is typical of other systems in the region. We identified 8 overstory and 26 understory communities using multivariate analyses. Young bar surfaces (5-20 yrs) were dominated by willow, red alder, and black cottonwood. Floodplains and transitional fluvial terraces (<90yrs) were generally dominated by alder and cottonwood. Mature terraces (>90yrs) were often dominated by big-leaf maple. Douglas fir occurred on both young and old floodplains and terraces. Overstory species composition was more stable from 2005 to 2010

We estimated the population size of migrating Alabama shad Alosa alabamae below Jim Woodruff Lock and Dam in the Apalachicola River (located in the central panhandle of northwestern Florida) using mark-recapture and relative abundance techniques. After adjustment for tag loss, emigration, and mortality, the population size was estimated as 25,935 (95% confidence interval, 17,715-39,535) in 2005, 2,767 (838-5,031) in 2006, and 8,511 (5,211-14,674) in 2007. The cumulative catch rate from boat electrofishing averaged 20.47 Alabama shad per hour in 2005, 6.10 per hour in 2006, and 13.17 per hour in 2007. The relationship between population size (N) and electrofishing catch per unit effort (CPUE) was modeled by the equation N = -9008.2 + (electrofishing CPUE X 1616.4). Additionally, in 2007 the hook-and-line catch rate averaged 1.94 Alabama shad per rod hour. A predictive model relating the population size and hook-and-line CPUE of spawning American shad A. sapidissima was applied to Alabama shad hook-and-line CPUE and produced satisfactory results. Recent spawning populations of Alabama shad in the Apalachicola River are low relative to American shad populations in other southeastern U.S. rivers. ?? Copyright by the American Fisheries Society 2008.

... Colorado RiverDam Fund. 431.7 Section 431.7 Public Lands: Interior Regulations Relating to Public Lands... management of the Colorado RiverDam Fund. Reclamation is responsible for the repayment of the Project and the administration of the Colorado RiverDam Fund and the Lower Colorado River Basin Development...

Northern squawfish Ptychocheilus oregonensis movements were monitored downstream of two lower Snake Riverdams during the juvenile salmonid migrations of 1992 and 1993. During a high flow year in 1993, the abundance of squawfish in the tailrace of Lower Granite Dam peaked in July, after the majority of juveniles had moved past Lower Granite Dam, and peak abundance was inversely related to river discharge. Few squawfish moved into the tailrace of Ice Harbor Dam in 1993 because of the extended period of spill. Distributions of squawfish in the tailrace of Lower Granite Dam varied between and within years and shifted in response to changing prey densities, flow patterns, water temperature, and diel cycles, but fish consistently used low velocity habitats. Data from Ice Harbor Dam is less extensive, but squawfish distributions there appeared to be affected by changing flow patterns and fish used low velocity habitats. The changes in distribution and abundance of squawfish in tailrace areas are evidence that predation on seaward migrating salmonids depends on the timing of migration and size and timing of runoff. Juvenile salmonids migrating in the spring and early summer will probably be less affected by squawfish predation in tailrace areas than salmon that migrate later in the summer.

1. SNAKE RIVER VALLEY IRRIGATION DISTRICT DAM, VIEW OF NORTH ELEVATION OF INTAKE ON EAST SIDE OF DAM - Snake River Valley Irrigation District, East Side of Snake River (River Mile 796), Shelley, Bingham County, ID

8. VIEW OF DAM 83, SHOWING OLD SOURIS RIVER CHANNEL FROM THE DOWNSTREAM FACE OF THE DAM WITH POND A IN THE BACKGROUND, LOOKING SOUTH - Upper Souris National Wildlife Refuge, Dam 83, Souris River Basin, Foxholm, Surrey (England), ND

downstream using LiDAR and GCD to determine whether a sediment pulse related to dam removal could be distinguished downstream. A simple DoD with no error propagation was completed for the entire length of the river channel. Downstream from the former dam the river enters a 7 km bedrock gorge where no deposition was documented. In the ½-km reach immediately downstream from the gorge deposition appeared on river banks and in-channel bars 1-3 years after dam removal. Beyond this reach, the sediment pulse related to removal could not be readily distinguished from normal river processes. However, each segment of the 40-km study reach downstream of the dam shows net sediment deposition during the 5-year study period.

... the administration of the Colorado RiverDam Fund and the Lower Colorado River Basin Development Fund... River Basin Project Act; (5) Transfers to the Lower Colorado River Basin Development Fund and subsequent... Colorado RiverDam Fund. 431.7 Section 431.7 Public Lands: Interior Regulations Relating to Public......

... the administration of the Colorado RiverDam Fund and the Lower Colorado River Basin Development Fund... River Basin Project Act; (5) Transfers to the Lower Colorado River Basin Development Fund and subsequent... Colorado RiverDam Fund. 431.7 Section 431.7 Public Lands: Interior Regulations Relating to Public......

... the administration of the Colorado RiverDam Fund and the Lower Colorado River Basin Development Fund... River Basin Project Act; (5) Transfers to the Lower Colorado River Basin Development Fund and subsequent... Colorado RiverDam Fund. 431.7 Section 431.7 Public Lands: Interior Regulations Relating to Public......

Egypt's High Aswan Dam on the Nile River at the first cataracts, Nile River, (24.0N, 33.0E) was completed in 1971 to provide cheap hydroelectric power and to regulate the historically uneven flow of the Nile River. The contrast between the largely base rock desert east of the Nile versus the sand covered desert west of the river and the ancient irrigated floodplain downstream from the damsite is clearly shown.

The Missouri River has had a long history of anthropogenic modification with considerable impacts on river and riparian ecology, form, and function. During the 20th century, several large dam-building efforts in the basin served the needs for irrigation, flood control, navigation, and the generation of hydroelectric power. The managed flow provided a range of uses, including recreation, fisheries, and habitat. Fifteen dams impound the main stem of the river, with hundreds more on tributaries. Though the effects of dams and reservoirs are well-documented, their impacts have been studied individually, with relatively little attention paid to their interaction along a river corridor. We examine the morphological and sedimentological changes in the Upper Missouri River between the Garrison Dam in ND (operational in 1953) and Oahe Dam in SD (operational in 1959). Through historical aerial photography, stream gage data, and cross sectional surveys, we demonstrate that the influence of the upstream dam is still a major control of river dynamics when the backwater effects of the downstream reservoir begin. In the “Anthropocene”, dams are ubiquitous on large rivers and often occur in series, similar to the Garrison Dam Segment. We propose a conceptual model of how interacting dams might affect river geomorphology, resulting in distinct and recognizable morphologic sequences that we term “Inter-Dam sequence” characteristic of major rivers in the US.

Rivers carved into uplifted plateaus are commonly disrupted by discrete events from the surrounding landscape, such as lava flows or large mass movements. These disruptions are independent of slope, basin area, or channel discharge, and can dominate aspects of valley morphology and channel behavior for many kilometers. We document and assess the effects of one type of disruptive event, lava dams, on river valley morphology and incision rates at a variety of time scales, using examples from the Owyhee River in southeastern Oregon. Six sets of basaltic lava flows entered and dammed the river canyon during two periods in the late Cenozoic ca. 2 Ma–780 ka and 250–70 ka. The dams are strongly asymmetric, with steep, blunt escarpments facing up valley and long, low slopes down valley. None of the dams shows evidence of catastrophic failure; all blocked the river and diverted water over or around the dam crest. The net effect of the dams was therefore to inhibit rather than promote incision. Once incision resumed, most of the intracanyon flows were incised relatively rapidly and therefore did not exert a lasting impact on the river valley profile over time scales >106 yr. The net long-term incision rate from the time of the oldest documented lava dam, the Bogus Rim lava dam (≤1.7 Ma), to present was 0.18 mm/yr, but incision rates through or around individual lava dams were up to an order of magnitude greater. At least three lava dams (Bogus Rim, Saddle Butte, and West Crater) show evidence that incision initiated only after the impounded lakes filled completely with sediment and there was gravel transport across the dams. The most recent lava dam, formed by the West Crater lava flow around 70 ka, persisted for at least 25 k.y. before incision began, and the dam was largely removed within another 35 k.y. The time scale over which the lava dams inhibit incision is therefore directly affected by both the volume of lava forming the dam and the time required for sediment

The presence of large dams affects habitat availability, often regarded as the primary factor that limits population and community recovery in rivers. Physical habitat is often targeted in restoration, but there is often a paucity of useful information. Habitat degradation has reduced the complexity and connectivity of the Mediterranean streams in Spain. These changes have diminished the historical range of the endangered Júcar nase, Parachondrostoma arrigonis (Steindachner, 1866), isolated the populations of this species, and probably contributed to its risk of extinction. In the Júcar River basin (Spain), where this fish is endemic, the populations are mainly restricted to the river Cabriel, which is fragmented in two segments by the large dam of Contreras. In this river, 3 main lines of research were developed from 2006 to 2008, i.e., microhabitat suitability, mesohabitat suitability, and water temperature, in order to relate such kind of variables with the flow regime. The main goal of the research project, funded by the Spanish Ministry of Environment, was to detect the main reasons of the species decline, and to propose dam operation improvements to contribute to the recovery of the species. The flow and water temperature regimes were also studied in the river Cabriel, upstream and downstream the large dam of Contreras. During the three years of study, below the dam it was observed a small and not significant variation in the proportions of slow and fast habitats; the regulated flow regime was pointed out as the main reason of such variations. At the microhabitat scale, optimal ranges for average depth and velocity were defined; these data allowed us to develop an estimation of weighted useable area under natural and regulated conditions. The Júcar nase were found majorly at depths no greater than 1,15 meters with slow water velocities. It was possible to observe a clear alteration of the flow and water temperature regime below the dam, due to the cold

More than 70,000 large dams have been built worldwide. With growing water stress and demand for energy, this number will continue to increase in the foreseeable future. Damming greatly modifies the ecological functioning of river systems. In particular, dam reservoirs sequester nutrient elements and, hence, reduce downstream transfer of nutrients to floodplains, lakes, wetlands, and coastal marine environments. Here, we quantify the global impact of dams on the riverine fluxes and speciation of the limiting nutrient phosphorus (P), using a mechanistic modeling approach that accounts for the in-reservoir biogeochemical transformations of P. According to the model calculations, the mass of total P (TP) trapped in reservoirs nearly doubled between 1970 and 2000, reaching 42 Gmol y(-1), or 12% of the global river TP load in 2000. Because of the current surge in dam building, we project that by 2030, about 17% of the global river TP load will be sequestered in reservoir sediments. The largest projected increases in TP and reactive P (RP) retention by damming will take place in Asia and South America, especially in the Yangtze, Mekong, and Amazon drainage basins. Despite the large P retention capacity of reservoirs, the export of RP from watersheds will continue to grow unless additional measures are taken to curb anthropogenic P emissions. PMID:26644553

More than 70,000 large dams have been built worldwide. With growing water stress and demand for energy, this number will continue to increase in the foreseeable future. Damming greatly modifies the ecological functioning of river systems. In particular, dam reservoirs sequester nutrient elements and, hence, reduce downstream transfer of nutrients to floodplains, lakes, wetlands, and coastal marine environments. Here, we quantify the global impact of dams on the riverine fluxes and speciation of the limiting nutrient phosphorus (P), using a mechanistic modeling approach that accounts for the in-reservoir biogeochemical transformations of P. According to the model calculations, the mass of total P (TP) trapped in reservoirs nearly doubled between 1970 and 2000, reaching 42 Gmol y−1, or 12% of the global river TP load in 2000. Because of the current surge in dam building, we project that by 2030, about 17% of the global river TP load will be sequestered in reservoir sediments. The largest projected increases in TP and reactive P (RP) retention by damming will take place in Asia and South America, especially in the Yangtze, Mekong, and Amazon drainage basins. Despite the large P retention capacity of reservoirs, the export of RP from watersheds will continue to grow unless additional measures are taken to curb anthropogenic P emissions. PMID:26644553

After years of planning for the largest project of its kind, the Department of the Interior will begin removal of two dams on the Elwha River, Washington, in September 2011. For nearly 100 years, the Elwha and Glines Canyon Dams have disrupted natural processes, trapping sediment in the reservoirs and blocking fish migrations, which changed the ecology of the river downstream of the dams. All five Pacific salmon species and steelhead-historically present in large numbers-are locally extirpated or persist in critically low numbers. Upstream of the dams, more than 145 kilometers of pristine habitat, protected inside Olympic National Park, awaits the return of salmon populations. As the dams are removed during a 2-3 year project, some of the 19 million cubic meters of entrapped sediment will be carried downstream by the river in the largest controlled release of sediment into a river and marine waters in history. Understanding the changes to the river and coastal habitats, the fate of sediments, and the salmon recolonization of the Elwha River wilderness will provide useful information for society as future dam removals are considered.

This report documents a review of the hydraulic and sediment-transport models developed by the City of Salisbury, Alcoa Power Generating, Inc., and the Federal Energy Regulatory Commission to address issues of flooding and sedimentation in the vicinity of Salisbury's water-supply intake 19.4 miles upstream from High Rock Dam. The objective of the review was to determine if the modeling results submitted by Salisbury clearly demonstrate that the presence of High Rock Dam has led to an increase in water levels at Salisbury facilities or, conversely, if the documents of Alcoa Power Generating, Inc., demonstrate that High Rock Dam has not had an effect on water levels at Salisbury facilities. No new data were collected as a part of the review, and the models developed by involved parties were not tested during the review. Some historical discharge-measurement notes and previously published reports were checked as part of the review. The one-dimensional hydraulic modeling results submitted by Alcoa Power Generating, Inc., did not assess the effects of changes in bathymetry on changes in flood levels at Salisbury's facilities because pre-impoundment conditions were not simulated. Hydraulic modeling performed by consultants for the City of Salisbury seems to indicate that both the presence of the dam in the absence of any post-impoundment sedimentation and changes in bathymetry between pre-impoundment and 1997 conditions have resulted in increased water levels relative to pre-impoundment conditions at Salisbury facilities on the Yadkin River for a fairly wide range of flows. The degree to which the dam and the changes in bathymetry have affected flood levels at the Salisbury facilities relative to pre-impoundment conditions is open to discussion because of uncertainty in topographic/bathymetric data and the absence of calibration and sensitivity testing of the hydraulic models. None of the three hydraulic models appears to have been calibrated to or tested against

3. NORTH SIDE OF DIVERSION DAM ON THE SNAKE RIVER SHOWING HEADGATE ON THE NORTH BANK. VIEW IS TO THE NORTH-NORTHWEST. - Snake River Ditch, Headgate on north bank of Snake River, Dillon, Summit County, CO

2. UPSTREAM SIDE OF DIVERSION DAM ON THE SNAKE RIVER, LOOKING SOUTH-SOUTHWEST. NOTE BANK REINFORCEMENT ON LEFT AND SPILLWAY ON RIGHT. - Snake River Ditch, Headgate on north bank of Snake River, Dillon, Summit County, CO

We examined the effects of the Zemko Dam removal on the Eightmile River system in Salem, Connecticut, USA. The objective of this research was to quantify spatiotemporal variation in fish community composition in response to small dam removal. We sampled fish abundance over a 6-year period (2005-2010) to quantify changes in fish assemblages prior to dam removal, during drawdown, and for three years following dam removal. Fish population dynamics were examined above the dam, below the dam, and at two reference sites by indicator species analysis, mixed models, non-metric multidimensional scaling, and analysis of similarity. We observed significant shifts in fish relative abundance over time in response to dam removal. Changes in fish species composition were variable, and they occurred within 1 year of drawdown. A complete shift from lentic to lotic fishes failed to occur within 3 years after the dam was removed. However, we did observe increases in fluvial and transition (i.e., pool head, pool tail, or run) specialist fishes both upstream and downstream from the former dam site. Our results demonstrate the importance of dam removal for restoring river connectivity for fish movement. While the long-term effects of dam removal remain uncertain, we conclude that dam removals can have positive benefits on fish assemblages by enhancing river connectivity and fluvial habitat availability. PMID:25022888

Populations of paddlefish Polyodon spathula have been adversely affected by dams that can block their movements. Unlike high-head dams that preclude fish passage (unless they are equipped with fishways), the dams on the upper Mississippi River are typically low-head dams with bottom release gates that may allow fish passage under certain conditions. We evaluated the relation of dam head and river discharge to the passage of radio-tagged paddlefish through dams in the upper Mississippi River. Radio transmitters were surgically implanted into 71 paddlefish from Navigation Pools 5A and 8 of the upper Mississippi River and from two tributary rivers during fall 1994 through fall 1996. We tracked paddlefish through September 1997 and documented 53 passages through dams, 20 upstream and 33 downstream. Passages occurred mostly during spring (71%) but also occurred sporadically during summer and fall (29%). Spring passages varied among years in response to hydrologic conditions. We evaluated patterns in upstream and downstream passages with Cox proportional hazard regression models. Model results indicated that dam head height strongly affected the upstream passage of paddlefish but not the downstream passage. Several paddlefish, however, passed upstream through a dam during periods when the minimum head at the dam was substantial ( greater than or equal to 1m). In these cases, we hypothesize that paddlefish moved upstream through the lock chamber.

Information about the composition and relative abundance of fish species was collected by a rotary screw trap and backpack electrofishing in the lower White Salmon River, Washington. The information was collected downstream of Condit Dam, which is at river kilometer (rkm) 5.2, and is proposed for removal in October 2011. A rotary screw trap was installed in the White Salmon River at rkm 1.5 and operated from March through June during 2006-09. All captured fish were identified to species and enumerated. Daily subsets of fish were weighed, measured, and fin clipped for a genetic analysis by the U.S. Fish and Wildlife Service. *Fall Chinook salmon (Oncorhynchus tshawytscha) were captured in the highest numbers (n=18, 640), and were composed of two stocks: tule and upriver bright. Almost all captured fall Chinook salmon were age-0, with only 16 (0.09 percent) being age-1 or older. *Tule fall Chinook salmon, the native stock, generally out-migrated from mid-March through early April. The tule stock was the more abundant fall Chinook salmon subspecies, comprising 85 percent of those captured in the trap. *Upriver bright fall Chinook salmon comprised 15 percent of the Chinook salmon catch and generally out-migrated from late May to early June. *Coho salmon (O. kisutch) and steelhead trout (O. mykiss) were captured by the rotary screw trap in all years. Coho salmon were caught in low numbers (n=661) and 69 percent were age-0 fish. Steelhead were slightly more abundant (n=679) than coho salmon and 84 percent were age-1 or older fish. Trap efficiency estimates varied widely (range, 0-10 percent) by species, fish size, and time of year. However, if we use only the estimates from efficiency tests where more than 300 wild age-0 Chinook salmon were released, there was a mean trapping efficiency of 1.4 percent (n=4, median, 1.3 percent, range, 0.3-2.4 percent) during the tule out-migration period, and a mean trapping efficiency of 0.8 percent (n=2, range, 0.3-1.2 percent) during

The Souhegan River is a tributary of the Merrimack River that drains a 443 km2 watershed in southern New Hampshire. The lowermost barrier on the Souhegan River was the ~4-m high Merrimack Village Dam (MVD, ~500 m upstream of the confluence with the Merrimack River), which was breached and removed starting on August 6, 2008. The MVD was built in 1906 at a location where various dams have existed since the 18th century. Based on a pre-removal sediment-thickness survey, the MVD impounded at least 62,000 m3 of sediment, mostly sand. We use a May 2008 ground penetrating radar survey of the impoundment to better constrain this sediment volume and stratigraphy. We also use historical maps and aerial photographs to estimate the possible extent of dam-influenced deposition at the site. We use 12 monumented cross sections, longitudinal profiles, repeat photography, and sediment samples to document the response of the Souhegan River to the removal of the MVD. Our study is part of the first full application of a recently published guide for stream barrier removal monitoring. Prior to dam removal, in August 2007 and June 2008, we surveyed the cross sections and longitudinal profile. We conducted re-surveys after removal in August and October 2008, and again in July and August 2009. Comparison between pre- and post-removal surveys shows that, in a 495-m reach upstream of the former location of the MVD, the Souhegan River eroded a net 38,100 m3 (47,900 metric tons) of sediment. This response began with rapid (hours to days) incision of a narrow channel, exhuming in some places bedrock and boulders that likely formed the pre-dam riverbed. Over the year since dam removal, the channel has widened by bank erosion but this process is limited by root strength and recruitment of large woody debris in the riparian zone of the former impoundment. Downstream of the former dam location, during the first days after removal, a sand deposit up to 1.0 to 3.5 m thick, or approximately 18,500 m3

Like many rivers in the western U.S., the Elwha River, Washington, has changed substantially over the past century in response to natural and human forcing. The lower river is affected by two upstream dams that are slated for removal as part of a major river restoration effort. In preparation for studying the effects of dam removal, we present a comprehensive field and aerial photographic analysis of dam influence on an anabranching, gravel-bed river. Over the past century with the dams in place, loss of the upstream sediment supply has caused spatial variations in the sedimentary and geomorphic character of the lower Elwha River channel. Bed sediment is armored and better sorted than on the naturally evolving bed upstream of the dams. On time scales of flood seasons, the channel immediately below the lower dam is fairly stable, but progresses toward greater mobility downstream such that the lowermost portion of the river responded to a recent 40-year flood with bank erosion and bed-elevation changes on a scale approaching that of the natural channel above the dams. In general, channel mobility in the lowest 4 km of the Elwha River has not decreased substantially with time. Enough fine sediment remains in the floodplain that – given sufficient flood forcing – the channel position, sinuosity, and braiding index change substantially. The processes by which this river accesses new fine sediment below the dams (rapid migration into noncohesive banks and avulsion of new channels) allow it to compensate for loss of upstream sediment supply more readily than would a dammedriver with cohesive banks or a more limited supply of alluvium. The planned dam removal will provide a valuable opportunity to evaluate channel response to the future restoration of natural upstream sediment supply.

Process dynamics in fluvial-based dryland environments are highly complex with fluvial, aeolian, and alluvial processes all contributing to landscape change. When anthropogenic activities such as dam-building affect fluvial processes, the complexity in local response can be further increased by flood- and sediment-limiting flows. Understanding these complexities is key to predicting landscape behavior in drylands and has important scientific and management implications, including for studies related to paleoclimatology, landscape ecology evolution, and archaeological site context and preservation. Here we use multi-temporal LiDAR surveys, local weather data, and geomorphological observations to identify trends in site change throughout the 446-km-long semi-arid Colorado River corridor in Grand Canyon, Arizona, USA, where archaeological site degradation related to the effects of upstream dam operation is a concern. Using several site case studies, we show the range of landscape responses that might be expected from concomitant occurrence of dam-controlled fluvial sand bar deposition, aeolian sand transport, and rainfall-induced erosion. Empirical rainfall-erosion threshold analyses coupled with a numerical rainfall–runoff–soil erosion model indicate that infiltration-excess overland flow and gullying govern large-scale (centimeter- to decimeter-scale) landscape changes, but that aeolian deposition can in some cases mitigate gully erosion. Whereas threshold analyses identify the normalized rainfall intensity (defined as the ratio of rainfall intensity to hydraulic conductivity) as the primary factor governing hydrologic-driven erosion, assessment of false positives and false negatives in the dataset highlight topographic slope as the next most important parameter governing site response. Analysis of 4+ years of high resolution (four-minute) weather data and 75+ years of low resolution (daily) climate records indicates that dryland erosion is dependent on short

Riverdamming leads to strong hydromorphological alterations of the watercourse, consequently affecting river vegetation pattern. A multitemporal and spatial analysis of the dam effect on composition, structure and dynamic of the upstream vegetation was performed on Tiber River at Nazzano-dam (Rome). The main research questions were as follows: How does plant landscape vary over time and along the river? Where does the dam effect on vegetation end? How does naturalistic importance of the vegetation affected by damming change over time? Data collection was performed mapping the vegetation in aerial photos related to the period before (1944), during (1954) and after dam construction (1984, 2000). The plant landscape has significantly changed over time and along the river, particularly as a result of the dam construction (1953). The major vegetation changes have involved riparian forests and macrophytes. Dam effect on vegetation is evident up to 3 km, and gradually decreases along an attenuation zone for about another 3 km. Despite the fact that the damming has caused strong local hydromorphological modification of the river ecosystem transforming it into a sub-lacustrine habitat, it has also led to the formation of wetlands of considerable naturalistic importance. Indeed, in these man-made wetlands, optimal hydrological conditions have been created by favouring both the expansion of pre-existing riparian communities and the rooting of new aquatic communities, albeit typical of lacustrine ecosystems. Some of these plant communities have become an important food resource, refuge or nesting habitats for aquatic fauna, while others fall into category of Natura 2000 habitats. Therefore, riverdamming seems to have indirectly had a "favourable" effect for habitat conservation and local biodiversity. PMID:25920677

Dam decommissioning has become an important means for removing unsafe or obsolete dams and for restoring natural fluvial processes, including discharge regimes, sediment transport, and ecosystem connectivity [Doyle et al., 2003]. The largest dam-removal project in history began in September 2011 on the Elwha River of Washington State (Figure 1a). The project, which aims to restore the river ecosystem and increase imperiled salmon populations that once thrived there, provides a unique opportunity to better understand the implications of large-scale river restoration.

Reservoirs behind dams act as deposition sites for much of the bed-material load being transported by rivers. As a result, the water exiting dams is relatively free of sediment and the river flow is well below the transport capacity for bed-material. Because of this, rivers flowing downstream from dams tend to erode into their beds. This occurrence is well documented in gravel-bed rivers, but has not been as completely studied in sand-bed channels, such as the lower Trinity River, Texas. Sediment mining from the bed of a gravel river acts to coarsen the surface layer until the armoring shuts off any further bed erosion. This armoring control on the sediment discharge is not effective in a sand bed river. The abundant supply of sediment in a sand bed alluvial river results in a unique response: the river bed is scoured until sediment transport capacity is reached. In the lower Trinity River the consequences of this scouring and bed-sediment mining are channel bed lowering, channel wall steepening, and reduced rates of lateral migration, as well as bed-sediment coarsening and deflation in the total volume of sediment constituting bars. The process of bed incision produces a convex long profile for the river segment influenced by the dam. After 40 years of impoundment the channel immediately downstream of the dam has incised five to seven meters and dam-influenced adjustments to the geomorphology of the river are observed for 50 to 60 river kilometers downstream. The channel downstream of this zone appears unaffected by the dam. Over time the river bed continues to erode and the zone of dam influence expands downstream. In this paper we present a one-dimensional morphodynamic model that estimates the adjustment in channel profile elevation through time due to the dam's retention of sediment. Model output matches the field measurements of physical changes to the river channel. Results of the model and physical observations explain the sediment transport dynamics

Regional assessment of cumulative impacts of dams on riverine fish assemblages provides resource managers essential information for dam operation, potential dam removal, river health assessment and overall ecosystem management. Such an assessment is challenging because characteristics of fish assemblages are not only affected by dams, but also influenced by natural variation and human-induced modification (in addition to dams) in thermal and flow regimes, physicochemical habitats and biological assemblages. This study evaluated the impacts of dams on river fish assemblages in the non-impoundment sections of rivers in the states of Michigan and Wisconsin using multiple fish assemblage indicators and multiple approaches to distinguish the influences of dams from those of other natural and human-induced factors. We found that environmental factors that influence fish assemblages in addition to dams should be incorporated when evaluating regional effects of dams on fish assemblages. Without considering such co-influential factors, the evaluation is inadequate and potentially misleading. The role of dams alone in determining fish assemblages at a regional spatial scale is relatively small (explained less than 20% of variance) compared with the other environmental factors, such as river size, flow and thermal regimes and land uses jointly. However, our results do demonstrate that downstream and upstream dams can substantially modify fish assemblages in the non-impoundment sections of rivers. After excluding river size and land-use influences, our results clearly demonstrate that dams have significant impacts on fish biotic-integrity and habitat-and-social-preference indicators. The influences of the upstream dams, downstream dams, distance to dams, and dam density differ among the fish indicators, which have different implications for maintaining river biotic integrity, protecting biodiversity and managing fisheries. ?? 2010 John Wiley & Sons, Ltd.

Regional assessment of cumulative impacts of dams on riverine fish assemblages provides resource managers essential information for dam operation, potential dam removal, river health assessment and overall ecosystem management. Such an assessment is challenging because characteristics of fish assemblages are not only affected by dams, but also influenced by natural variation and human-induced modification (in addition to dams) in thermal and flow regimes, physicochemical habitats and biological assemblages. This study evaluated the impacts of dams on river fish assemblages in the non-impoundment sections of rivers in the states of Michigan and Wisconsin using multiple fish assemblage indicators and multiple approaches to distinguish the influences of dams from those of other natural and human-induced factors. We found that environmental factors that influence fish assemblages in addition to dams should be incorporated when evaluating regional effects of dams on fish assemblages. Without considering such co-influential factors, the evaluation is inadequate and potentially misleading. The role of dams alone in determining fish assemblages at a regional spatial scale is relatively small (explained less than 20% of variance) compared with the other environmental factors, such as river size, flow and thermal regimes and land uses jointly. However, our results do demonstrate that downstream and upstream dams can substantially modify fish assemblages in the non-impoundment sections of rivers. After excluding river size and land-use influences, our results clearly demonstrate that dams have significant impacts on fish biotic-integrity and habitat-and-social-preference indicators. The influences of the upstream dams, downstream dams, distance to dams, and dam density differ among the fish indicators, which have different implications for maintaining river biotic integrity, protecting biodiversity and managing fisheries.

This report describes a study of survival and migration behavior of radio-tagged juvenile coho salmon (Oncorhynchus kisutch) in the Klamath River, northern California, in 2007. This was the third year of a multi-year study with the goal of determining the effects of discharge at Iron Gate Dam (IGD) on survival of juvenile coho salmon downstream. Survival and factors affecting survival were estimated in 2006 and 2007 after work in 2005 showed radio telemetry could be used effectively. The study has included collaborative efforts among U.S. Geological Survey (USGS), U.S. Fish and Wildlife Service (USFWS), the Karuk and Yurok Tribal Fisheries Departments, and the U.S. Bureau of Reclamation. The objectives of the study included: (1) estimating the survival of wild and hatchery juvenile coho salmon in the Klamath River downstream of Iron Gate Dam, determining the effects of discharge and other covariates on juvenile coho salmon survival (2) and migration (3), and (4) determining if fish from Iron Gate Hatchery (IGH) could be used as surrogates for the limited source of wild fish. We have been able to meet the first objective by estimating the survivals of hatchery and wild fish (when available) downstream of IGD. We have not yet met the second or third objectives, because we have been unable to separate effects of discharge from other environmental variables as they pertain to the survival or migration of juvenile coho salmon. This was foreseen when the study began, as it was known there would likely be no experimental discharges. A multi-year analysis will be conducted after the data for the third planned year are available. The fourth objective was initiated in 2006, but wild fish were not available in 2007. The next year wild fish may be available is in 2009, based on their 3-year cycle of abundance. River discharges during the 2007 study period (April 10 through July 28, 2007) were below average compared to the period of record beginning in 1962. Average daily

1. Costa Rica has recently experienced a rapid proliferation of dams for hydropower on rivers draining its northern Caribbean slope. In the Sarapiqui River Basin, eight hydropower plants were built between 1990 and 1999 and more projects are either under construction or proposed. The majority of these dams are small (< 15 m tall) and operate as water diversion projects. 2. While the potential environmental effects of individual projects are evaluated prior to dam construction, there is a need for consideration of the basin-scale ecological consequences of hydropower development. This study was a first attempt to quantify the extent of river fragmentation by dams in the Sarapiqui River Basin. 3. Using simple spatial analyses, the length of river upstream from dams and the length of de-watered reaches downstream from dams was measured. Results indicated that there are currently 306.8 km of river (9.4% of the network) upstream from eight existing dams in the Sarapiqui River Basin and 30.6 km of rivers (0.9% of the network) with significantly reduced flow downstream from dams. Rivers upstream from dams primarily drain two life zones: Premontane Rain Forest (107.9km) and Lower Montane Rain Forest (168.2km). 4. Simple spatial analyses can be used as a predictive or planning tool for considering the effects of future dams in a basin-scale context. In the Sarapiqui River Basin, we recommend that future dam projects be constructed on already dammedrivers to minimize additional river fragmentation and to protect remaining riverine connectivity.

We compared the effects of water resource development on migratory fish in two North American rivers using a descriptive approach based on four high-level indicators: (1) trends in abundance of Pacific salmon, (2) reliance on artificial production to maintain fisheries, (3) proportion of adult salmon that are wild- versus hatchery-origin, and (4) number of salmon populations needing federal protection to avoid extinction. The two rivers had similar biological and physical features but radically different levels of water resource development: the Fraser River has few dams and all are located in tributaries, whereas the Columbia River has more than 130 large mainstem and tributary dams. Not surprisingly, we found substantial effects of development on salmon in the Columbia River. We related the results to potential effects on migratory fish in the Mekong River where nearly 200 mainstem and tributary dams are installed, under construction, or planned and could have profound effects on its 135 migratory fish species. Impacts will vary with dam location due to differential fish production within the basin, with overall effects likely being greatest from 11 proposed mainstem dams. Minimizing impacts will require decades to design specialized fish passage facilities, dam operations, and artificial production, and is complicated by the Mekong's high diversity and productivity. Prompt action is needed by governments and fisheries managers to plan Mekong water resource development wisely to prevent impacts to the world's most productive inland fisheries, and food security and employment opportunities for millions of people in the region.

We compared the effects of water resource development on migratory fish in two North American rivers using a descriptive approach based on four high-level indicators: (1) trends in abundance of Pacific salmon, (2) reliance on artificial production to maintain fisheries, (3) proportion of adult salmon that are wild- versus hatchery-origin, and (4) number of salmon populations needing federal protection to avoid extinction. The two rivers had similar biological and physical features but radically different levels of water resource development: the Fraser River has few dams and all are located in tributaries, whereas the Columbia River has more than 130 large mainstem and tributary dams. Not surprisingly, we found substantial effects of development on salmon in the Columbia River. We related the results to potential effects on migratory fish in the Mekong River where nearly 200 mainstem and tributary dams are installed, under construction, or planned and could have profound effects on its 135 migratory fish species. Impacts will vary with dam location due to differential fish production within the basin, with overall effects likely being greatest from 11 proposed mainstem dams. Minimizing impacts will require decades to design specialized fish passage facilities, dam operations, and artificial production, and is complicated by the Mekong's high diversity and productivity. Prompt action is needed by governments and fisheries managers to plan Mekong water resource development wisely to prevent impacts to the world's most productive inland fisheries, and food security and employment opportunities for millions of people in the region. PMID:20924582

We studied spatiotemporal patterns of fish assemblage structure in the Neosho River, Kansas, a system impounded by low-head dams. Spatial variation in the fish assemblage was related to the location of dams that created alternating lotic and lentic stream reaches with differing fish assemblages. At upstream sites close to dams, assemblages were characterized by species associated with deeper, slower-flowing habitat. Assemblages at sites immediately downstream from dams had higher abundance of species common to shallow, swift-flowing habitat. Temporal variation in assemblage structure was stronger than spatial variation, and was associated with fish life history events such as spawning and recruitment, as well as seasonal changes in environmental conditions. Our results suggest that low-head dams can influence spatial patterns of fish assemblage structure in systems such as the Neosho River and that such assemblages also vary seasonally.

The impacts of dams in New England are especially acute as it possesses one of the highest densities of dams in the US, with the NID documenting more than 4,000 dams, and state agency records indicating that >14,000 dams are peppered throughout the landscape. This large number of dams contributes to pervasive watershed fragmentation, threatening the ecological integrity of rivers and streams, and in the case of old, poorly maintained structures, posing a risk to lives and property. These concerns have generated active dam removal efforts throughout New England. To best capture the geomorphic, hydrologic, and potential ecological effects of dam removal at a regional level, we have compiled a dataset of 127 removed dams in New England, which includes information about structural characteristics, georectified locations, and key watershed attributes (including basin size, distance to next upstream obstacle, and number of free-flowing river kms opened up). Our specific research questions address (1) what is the spatial distribution of removed dams and how does this pattern relate to stated management goals of restoring critical habitat for native resident freshwater and diadromous fish, (2) what are the structural or management commonalities in dam types that have been removed, and (3) what has been the incremental addition of free-flowing river length? Rather than reflecting an overall management prioritization strategy, results indicate that dam removals are characterized more by opportunistic removals. For example, despite a regional emphasis on diadromous fish protection and restoration, most removals are inland rather than coastal settings. Most of the removed dams were small (~ 45% < 4 m) although ~10% of the removed dams were 6-8 m high. However, despite the predominant removal of small dams, these dams were not restricted to headwater locations; most (38%) occurred in medium-sized watersheds having upstream drainage areas between 100-1,000 km2 with 8% formerly

Fish assemblages in rivers of the Midwestern United States are an important component of the region's natural resources and biodiversity. We characterized the physical environment and presence of dams in a series of reaches in three eastern Iowa rivers tributary to the Mississippi River and related these characteristics to the fish assemblages present. Some physical characteristics were similar among the 12 study reaches, whereas others differed substantially. We found a total of 68 species across the 12 study reaches; 56 in the Turkey River, 51 in the Maquoketa River and 50 in the Wapsipinicon River. Seventeen species could be described as ‘downstream-distributed’; 15 being found only in the lowest reach of one or more rivers and the other two being found only in the lowest reaches or two or more contiguous reaches including the lowest reach. Two species could be described as ‘upstream-distributed’, being found only in an uppermost reach. Non-metric multidimensional scaling ordination illustrated similarities among reaches, and five physical variables were significantly correlated with assemblage similarities. Catchment area and number of dams between reaches and the Mississippi River were strongly correlated with assemblage similarities, but the directions of their effects were opposite. Catchment area and number of dams were confounded. The collective evidence to date suggests that the pervasiveness of dams on rivers significantly alters fish assemblages, making underlying patterns of species change and relationships with naturally varying and human-influenced physical characteristics along a river's course difficult to discern.

The Zambezi River is the fourth largest river in Africa (after the Congo, Nile, and Niger), and it is the largest African river flowing into the Indian Ocean. The lower Zambezi in Mozambique is influenced by the presence of two very large reservoirs (Kariba dam and Cahora Bassa dam) that have modified the natural seasonal flows, as well as the sediment balance and morphology of the river. In particular, downstream of the Cahora Bassa reservoir down to the delta, no negligible effects are reported to take place, such as local scour, bank collapse, and shoreline progressive erosion (Davies et al., 2000; Beilfuss and Dos Santos, 2001). In order to quantify and possibly mitigate these effects, a simplified numerical model of the sediment transport and erosion/sedimentation phenomena along the lower Zambezi has been developed, capable to deal with the scanty and uncertain data available. Indeed, besides the systematic flow records at the dam sites and few occasional measurements of turbidity and bottom granulometry, only the Digital Elevation Model (DEM) of the river will be used for the model. The objective of this paper is to predict the present and future effects of the presence of the Kariba and Cahora Bassa dams on the downstream morphology, integrating the few coarse and nonsimultaneous data, somehow improving their overall quality. The model reproduces the time and space propagation of the disturbances, that confirm, with more generality, the qualitative response of the river to the constructions of dams, anticipated by various geomorphologists. In fact, the reduction of waterflow seems to have an immediate effect downstream by initially fostering the sediment deposition. Subsequently, the total interception of sediment by the dam slowly takes over and inverts this tendency. A slightly smaller aggradation (or slightly larger degradation) rate with respect to the natural conditions (no dams) seems to represent the dominant effect of damming in the long term

Construction and operation of large dams in river basins have trapped large volumes of freshwater and sediment, which not only alters the natural seasonal rhythm of river hydrological cycles, but also creates a disconnection between rivers and their deltas. As a result, the water and sediment discharged to the coastal ocean have been greatly reduced, which triggers profound responses in coastal region including delta destruction, accelerated rise of relative sea level and changes in coastal primary production. The Yellow River has been a well documented system with significant impacts of dam regulation. Recent sediment load and freshwater (2002-2012) delivered to the sea have been reduced to 0.16 billion tones per year and 17.9 km3/yr, approximately 13% and 34% of those in 1950s-1960s, a period without significant dam impacts. Dam interception and dam-facilitated water regulation play a dominated role in reducing the flux of water and sediment to the sea, as well as in changing the grain-size composition of sediment. Consequently, the process of estuarine sediment dynamics has changed and the delta has recently been converted into a destructive phase with strong coastal erosion due to insufficient rive sediment supply although the accretion of the active delta lobe was evident because of rapid local deposition of coarsening river sediment around the river mouth. The delta coast erosion has thus become a major source for sediment transport in the Bohai Sea and even to those in the Yellow Sea given the critical role of monsoonal climate on coastal resuspension and coastal currents. Delta erosion and subsidence have therefore accelerated the rate of relative sea-level rise, considerably higher than the global mean, which has put the mega-delta to be at risk. In addition, recent works have identified two peaks of chlorophyll-a within annual cycle in the delta coastal region, one of which is closely associated with the river delivery of nutrients transferred with

Dam removal is becoming more common in the United States as dams age and environmental concerns increase. Sediment management is an important part of many dam removal projects, but there are no commonly accepted methods to assess the level of risk associated with sediment stored behind dams. Therefore, the interagency Subcommittee on Sedimentation (SOS) is sponsoring the development of a decision framework for assessing sediment-related effects from dam removals. The decision framework provides guidance on the level of sediment data collection, analysis, and modeling needed for reservoir sediment management. The framework is based on criteria which scale the characteristics of the reservoir sediment to sediment characteristics of the river on which the reservoir is located. To assist with the framework development, workshops of invited technical experts from around the United States were convened October 2008 in Portland, Oregon and October 2009 in State College, Pennsylvania. The decision framework developed at these workshops is currently being validated with actual dam-removal case studies from across the United States including small, medium, and large reservoir sediment volumes. This paper provides the latest thinking on key components of the guidelines. The paper represents contributions from over 26 entities who have participated in the development of the guidelines. After completion of the case study application, the framework will be finalized and published.

This report describes the application of an unsteady, one-dimensional water-quality model to the Cumberland River below Wolf Creek Dam, Kentucky. A hydropower upgrade of Wolf Creek Dam and construction of a reregulation dam, located approximately 10 miles below Wolf Creek Dam, are under consideration. Simulations were conducted under unreregulated conditions and projected conditions following impoundment to provide information concerning the effect of the reregulation dam on water quality in the Cumberland River. Under the conditions simulated, the reregulation dam was predicted to have little impact on temporally averaged water temperatures or dissolved-oxygen concentrations. Temporal variations in water temperatures were retarded under reregulation conditions.

The U.S. Geological Survey is charged with monitoring the water and mineral resources of the United States. Beginning in 1889, the Survey established a network of water gaging stations across most of the country's rivers; some also measured sediment content of the water. Consequently, we now have valuable long-term data with which to track water supply, sediment transport, and the occurrence of floods. Many variables affect the flow of water from mountain brook to river delta. Some are short-term perturbations like summer thunderstorms. Others occur over a longer period of time, like the El Ninos that might be separated by a decade or more. We think of these variables as natural occurrences, but humans have exerted some of the most important changes -- water withdrawals for agriculture, inter-basin transfers, and especially the construction of an extensive system of dams. Dams have altered the flow of many of the Nation's rivers to meet societal needs. We expect floods to be contained. Irrigation is possible where deserts once existed. And water is released downstream not according to natural cycles but as dictated by a region's hour-by-hour needs for water or electricity. As a result, river channels below dams have changed dramatically. Depending on annual flow, flood peaks, and a river's sediment load, we might see changes such as sand building up in one channel, vegetation crowding into another, and extensive bank erosion in another. This Circular explores the emerging scientific arena of change in rivers below dams. This science tries first to understand and then anticipate changes to river beds and banks, and to riparian habitats and animal communities. To some degree, these downstream changes can be influenced by specific strategies of dam management. Scientists and resource managers have a duty to assemble this information and present it without bias to the rest of society. Society can then more intelligently choose a balance between the benefits and adverse

60. Aerial view looking southeast; Dundee Dam and Passaic River at center, Dundee Canal and headgates, guardlock, and former hydroelectric facility at right, Dundee Textile Mill between river and canal - Dundee Canal Industrial Historic District, Beginning at George Street in Passaic & extending north along Dundee Canal approximately 1.2 miles to Canal headgates opposite East Clifton Avenue in Clifton, Passaic, Passaic County, NJ

Surveys were conducted in 1995, 1996, and 1997 to assess community characteristics, population demography of dominant species, status of endangered species, and characteristics of nonindigenous populations of freshwater bivalves in the lower Ohio River. Data will be used to analyze impacts of construction and operation of a new lock and dam at River Mile (RM) 964.4. The greatest focus has been on a mussel bed just downstream of the project. Density categories of <20, 20 to 50, and >50 individuals per square meter are reasonable for delineating low-, moderate-, and high-density assemblages within this bed. Density >200 individuals per square meter is occasionally measured, but always describes a location heavily dominated by recent recruits. The native mussel community of the lower Ohio River is dominated by Fusconaia ebena. Dominance of this species was high at RM 967 (near Olmsted, IL), typically exceeding 80 percent of the community. At RM 957 (near Post Creek, IL), F. ebena is much less dominant (33 percent). Species richness is similar at both locations. The F. ebena population in the lower Ohio River is heavily dominated by a single-year class (probably 1990) of recent recruits. Prior to the exceptional recruitment in 1990, this population was dominated by a very abundant 1981 cohort.

Multiple dam passage during seaward migration is thought to reduce the subsequent survival of Snake River Chinook salmon. This hypothesis developed because juvenile Chinook salmon from the Snake River, the Columbia River's largest tributary, migrate >700 km through eight hydropower dams and have lower adult return rates than downstream populations that migrate through only 3 or 4 dams. Using a large-scale telemetry array, we tested whether survival of hatchery-reared juvenile Snake River spring Chinook salmon is reduced in the estuary and coastal ocean relative to a downstream, hatchery-reared population from the Yakima River. During the initial 750-km, 1-mo-long migration through the estuary and coastal ocean, we found no evidence of differential survival; therefore, poorer adult returns of Snake River Chinook may develop far from the Columbia River. Thus, hydrosystem mitigation efforts may be ineffective if differential mortality rates develop in the North Pacific Ocean for reasons unrelated to dam passage. PMID:23576733

The majority of the world's floodplains are dammed. Although some implications of dams for riverine ecology and for river channel morphology are well understood, there is less research on the impacts of dams on floodplain geomorphology. We review studies from dammed and undammed rivers and include influences on vertical and lateral accretion, meander migration and cutoff formation, avulsion, and interactions with floodplain vegetation. The results are synthesized into a conceptual model of the effects of dams on the major geomorphic influences on floodplain development. This model is used to assess the likely consequences of eight dam and flow regulation scenarios for floodplain geomorphology. Sediment starvation downstream of dams has perhaps the greatest potential to impact on floodplain development. Such effects will persist further downstream where tributary sediment inputs are relatively low and there is minimal buffering by alluvial sediment stores. We can identify several ways in which floodplains might potentially be affected by dams, with varying degrees of confidence, including a distinction between passive impacts (floodplain disconnection) and active impacts (changes in geomorphological processes and functioning). These active processes are likely to have more serious implications for floodplain function and emphasize both the need for future research and the need for an "environmental sediment regime" to operate alongside environmental flows. PMID:24587718

The majority of the world's floodplains are dammed. Although some implications of dams for riverine ecology and for river channel morphology are well understood, there is less research on the impacts of dams on floodplain geomorphology. We review studies from dammed and undammed rivers and include influences on vertical and lateral accretion, meander migration and cutoff formation, avulsion, and interactions with floodplain vegetation. The results are synthesized into a conceptual model of the effects of dams on the major geomorphic influences on floodplain development. This model is used to assess the likely consequences of eight dam and flow regulation scenarios for floodplain geomorphology. Sediment starvation downstream of dams has perhaps the greatest potential to impact on floodplain development. Such effects will persist further downstream where tributary sediment inputs are relatively low and there is minimal buffering by alluvial sediment stores. We can identify several ways in which floodplains might potentially be affected by dams, with varying degrees of confidence, including a distinction between passive impacts (floodplain disconnection) and active impacts (changes in geomorphological processes and functioning). These active processes are likely to have more serious implications for floodplain function and emphasize both the need for future research and the need for an “environmental sediment regime” to operate alongside environmental flows. PMID:24587718

Over the last century, the two dams blocked the upstream movement of anadromous fish to over 90% of the Elwha River watershed on the Olympic Peninsula of Washington State. These dams also restricted the downstream movement of sediment, wood, and other organic materials to the lower river and estuary. Populations of all Pacific salmon species and steelhead in the Elwha became critically low, habitat complexity decreased below the dams, and downstream coastal habitats became sediment starved. Simultaneous deconstruction of the two dams began in September 2011 was completed in September of 2014. The recent removal of the dams has been an opportunity to explore linkages among changes in sediment supply, salmonid populations, and ecosystem attributes. Preliminary findings focus on the delivery of millions of metric tonnes of sediment to the main river, its floodplain, and nearshore, the re-establishment of a natural wood delivery regime, the re-colonization of the upper watershed by anadromous fish, insights into functional relationships among salmonid populations and life history strategies, and the associated effects of all these elements on the aquatic and terrestrial foodwebs. This talk will provide an overview of the Elwha restoration project, and highlight recent changes observed during dam removal.

The phosphorus to silicon (P:Si) nutrient ratio is a key variable affecting ecosystem health in many aquatic environments. Riverdamming represents a major anthropogenic perturbation of natural material flows along the aquatic continuum, with the potential to profoundly modify absolute and relative nutrient availabilities in surface waters. In this study, a multi-tiered approach for estimating global nutrient retention in man-made reservoirs is presented. We illustrate its application to the global riverine flux of reactive Si, using a database of dissolved reactive Si (DSi) budgets for 24 natural lakes and 22 artificial reservoirs. The database includes information on bedrock geology, surface water pH, water residence time, reservoir age and function, climate, and trophic status. Statistical analyses (ANOVA, t-test, PCA, linear plus non-linear regressions) are used to identify the best predictors of DSi retention and delineate how reservoir properties modulate nutrient dynamics. Results indicate that (1) reservoirs retain significantly less DSi than natural lakes, and (2) the water residence time, reservoir age and function (e.g., hydroelectrical production, irrigation, flood control) are the main system variables controlling DSi retention by dams. Next, a biogeochemical Si model is used to reproduce the previously derived statistical trends for DSi retention. Calibration of the model yields a relationship that enables one to predict annual in-reservoir siliceous productivity as a function of the external reactive Si supply. The model further accounts for the transition from reservoirs where reactive Si retention is primarily due to burial of allochtonous Si to those where in-reservoir DSi uptake by diatoms dominates. Finally, the statistical and mechanistic relationships are extrapolated to estimate that 25-28 Tg SiO2 yr-1 are retained worldwide by dams, or 7% of the annual reactive Si load to watersheds. We are currently applying the same multi-tiered approach

Techniques for computing discharge are developed for Brandon Road Dam on the Des Plaines River and for Dresden Island, Marseilles, and Starved Rock Dams on the Illinois River. At Brandon Road Dam, streamflow is regulated by the operation of Tainter gates and headgates. At Dresden Island, Marseilles, and Starved Rock Dams, only Tainter gates are operated to regulate streamflow. The locks at all dams are equipped with culvert valves that are used to fill and empty the lock. The techniques facilitate determination of discharge at locations along the upper Illinois Waterway where no streamflow-gaging stations exist. The techniques are also useful for computing low flows when the water-surface slope between control structures on the river approaches zero and traditional methods of determining discharge based on slope are unsatisfactory. Two techniques can be used to compute discharge at the dams--gate ratings and tailwater ratings . A gate ratingdescribes the relation between discharge, gate opening, tailwater stage, and headwater stage. A tailwater rating describes the relation between tailwater stage and discharge. Gate ratings for Tainter gates at Dresden Island, Marseilles, and Starved Rock Dams are based on a total of 78 measurements of discharge that range from 569 to 86,400 cubic feet per second. Flood hydrographs developed from the gate ratings and Lockmaster records of gate opening and stage compare closely with streamflow records published for nearby streamflow-gaging stations. Additional measurements are needed to verify gate ratings for Tainter gates and headgates at Brandon Road Dam after the dam rehabilitation is completed. Extensive leakage past deteriorated headgates and sluice gates contributed to uncertainty in the ratings developed for this dam. A useful tailwater rating is developed for Marseilles Dam. Tailwater ratings for Dresden Island Dam and Starved Rock Dam are of limited use because of varying downstream channel-storage conditions. A tailwater

Dam construction has recently received new interest as an alternative and renewable source of energy, especially in developing countries, and as a means to provide water security in regions with naturally variable water flows. On the other hand, the negative effects from increased fragmentation of the world's large rivers through hydropower and irrigation dams is a matter of great concern for ecologists and conservationists. The main negative effects of dams result from their role as a barrier for migratory fish species, as well as the alteration of the natural flow regime owing to artificial water release schedules. While the trade-offs between these antagonistic effects are usually assessed locally by conducting environmental impact assessments at and in the vicinity of the construction site, the cumulative effects of multiple dams located in the same basin are generally neglected in such plans. To address the cumulative effects at the scale of large river networks, we developed a new impact assessment approach by combining state-of-the-art global scale hydrographic (HydroSHEDS) and hydrological models (WaterGAP) with a river routing scheme (HydroROUT). This combination enables modelers to simulate scenarios for historic, current and future conditions that allow for comparisons between the large river basins of the world. We derive indices that can describe the relative impact of individual and multiple dams regarding flow alteration and habitat fragmentation at a global scale. Our model also allows for the application of tailor-made weighting schemes to include information of eco-hydrological classifications, as well as species richness and diversity. Furthermore, we include natural barriers such as waterfalls, and examine their effect on river network connectivity. Results for the Greater Mekong Region show that ecosystem connectivity and flow alteration are most strongly affected by dams located at the mainstream rivers, particularly for basins where the main

Glen Canyon Dam, located on the Colorado River in northern Arizona, has affected the physical, biological and cultural resources of the river downstream in Grand Canyon. One of the impacts to the downstream physical environment that has important implications for the aquatic ecosystem is the transformation of the thermal regime from highly variable seasonally to relatively constant year-round, owing to hypolimnetic releases from the upstream reservoir, Lake Powell. Because of the perceived impacts on the downstream aquatic ecosystem and native fish communities, the Glen Canyon Dam Adaptive Management Program has considered modifications to flow releases and release temperatures designed to increase downstream temperatures. Here, we present a new model of monthly average water temperatures below Glen Canyon Dam designed for first-order, relatively simple evaluation of various alternative dam operations. The model is based on a simplified heat-exchange equation, and model parameters are estimated empirically. The model predicts monthly average temperatures at locations up to 421 km downstream from the dam with average absolute errors less than 0.58C for the dataset considered. The modelling approach used here may also prove useful for other systems, particularly below large dams where release temperatures are substantially out of equilibrium with meteorological conditions. We also present some examples of how the model can be used to evaluate scenarios for the operation of Glen Canyon Dam.

This report documents sampling and analytical methods and presents field data from a second year of an ongoing study on the Klamath River from Link RiverDam to Keno Dam in south central Oregon; this dataset will form the basis of a hydrodynamic and water quality model. Water quality was sampled weekly at six mainstem and two tributary sites from early April through early November, 2008. Constituents reported herein include field-measured water-column parameters (water temperature, pH, dissolved oxygen concentration, specific conductance); total nitrogen and phosphorus; particulate carbon and nitrogen; total iron; filtered orthophosphate, nitrite, nitrite plus nitrate, ammonia, organic carbon, and iron; specific UV absorbance at 254 nanometers; chlorophyll a; phytoplankton and zooplankton enumeration and species identification; and bacterial abundance and morphological subgroups. Sampling program results indicated: *Most nutrient and carbon concentrations were lowest in spring, increased starting in mid-June, remained elevated in the summer, and decreased in fall. Dissolved nitrite plus nitrate had a different seasonal cycle and was below detection or at low concentration in summer. *Although total nitrogen and total phosphorus concentrations did not show large differences from upstream to downstream, filtered ammonia and orthophosphate concentrations increased in the downstream direction and particulate carbon and particulate nitrogen generally decreased in the downstream direction. *Large bacterial cells made up most of the bacteria biovolume, though cocci were the most numerous bacteria type. Cocci, with diameters of 0.1 to 0.2 micrometers, were smaller than the filter pore sizes used to separate dissolved from particulate matter. *Phytoplankton biovolumes were dominated by diatoms in spring and by the blue-green alga Aphanizomenon flos-aquae after mid-June. Another blue-green, Anabaena flos-aquae, was noted in samples from late May to late June. Phytoplankton

Simple spatial analyses can be used as a predictive or planning tool for considering the effects of future dams in a basin-scale context. In the Sarapiquí River Basin, we recommend that future dam projects be constructed on already dammedrivers to minimize additional river fragmentation and to protect remaining riverine connectivity.

Low-head dam impoundments modify local habitat and alter fish assemblages; however, to our knowledge, the pattern of how fish assemblages in the impoundments relate to local habitat, tributary position, and dam characteristics is still unclear. We used data collected in 62 impoundments created by low-head dams in headwater streams of the Qingyi River, China, to examine relationships between fish assemblages and local habitat, tributary position, and dam characteristics. We also assessed the relative importance of the three groups of factors in determining fish species richness and composition. Linear regression models showed that fish species richness was related to substrate heterogeneity, confluence link, and dam number upstream. Redundancy analysis showed that fish species compositions were influenced by substrate heterogeneity, confluence link, dam height, dam numbers upstream and downstream. Overall, dam characteristics were more important in affecting fish species richness but less important in determining fish species composition than local habitat (i.e., substrate heterogeneity) and tributary position. Our results suggest that low-head dam may affect fish species richness in impoundments by modifying local habitat and constraining fish movement, and the relative abundances of those fish species may depend more on species habitat presences and stream size than on impoundment size and number. PMID:27029863

A substantial increase in fluvial sediment supply relative to transport capacity causes complex, large-magnitude changes in river and floodplain morphology downstream. Although sedimentary and geomorphic responses to sediment pulses are a fundamental part of landscape evolution, few opportunities exist to quantify those processes over field scales. We investigated the downstream effects of sediment released during the largest dam removal in history, on the Elwha River, Washington, USA, by measuring changes in riverbed elevation and topography, bed sediment grain size, and channel planform as two dams were removed in stages over two years. As 10.5 million t (7.1 million m3) of sediment was released from two former reservoirs, downstream dispersion of a sediment wave caused widespread bed aggradation of ~ 1 m (greater where pools filled), changed the river from pool-riffle to braided morphology, and decreased the slope of the lowermost river. The newly deposited sediment, which was finer than most of the pre-dam-removal bed, formed new bars (largely pebble, granule, and sand material), prompting aggradational channel avulsion that increased the channel braiding index by almost 50%. As a result of mainstem bed aggradation, floodplain channels received flow and accumulated new sediment even during low to moderate flow conditions. The river system showed a two- to tenfold greater geomorphic response to dam removal (in terms of bed elevation change magnitude) than it had to a 40-year flood event four years before dam removal. Two years after dam removal began, as the river had started to incise through deposits of the initial sediment wave, ~ 1.2 million t of new sediment (~ 10% of the amount released from the two reservoirs) was stored along 18 river km of the mainstem channel and 25 km of floodplain channels. The Elwha River thus was able to transport most of the released sediment to the river mouth. The geomorphic alterations and changing bed sediment grain size along

Lake Nasser, (24.0N, 33.0E) at the Aswan High Dam on the Nile River, in Egypt is the world's second largest artificial lake, extending 500 km, in length and about 5000 sq. km. in area. The lake has a storage capacity sufficient to irrigate farms in Egypt and Sudan year round allowing up to three harvests per year. Other benefits include year round river navagation, hydroelectric power, more fish harvests, reduced flooding and more industrial employment. opportunites.

13. Looking west down the Sugar River just above dam No. 3 with the Sullivan Machinery Co. Machine and Erecting Shops on the left, and the roof of the foundry complex just visible beyond the trees. From the headgates that still remain on the right, a 7.5' diameter penstock extended 1300' downstream along the north bank of the river to a powerhouse. - Claremont Village Industrial District, Between B, Claremont, Sullivan County, NH

Numerous large lava flows and mass movements have temporarily dammed the Owyhee River in southeastern Oregon at various temporal and spatial scales. These channel-encroaching events potentially play a significant role in creating and maintaining the geomorphic features of river canyons in uplifted volcanic terranes that compose a significant part of the western U.S. Abundant landslides and lava flows have the capacity to inhibit incision by altering channel slope, width, and bed character, and burying valley- bottom bedrock under exogenous material; or promote incision by generating cataclysmic floods through natural dam failures. The natural dams vary in their source, morphology, longevity and process of removal, which in turn affects the extent and duration of their impact on the river. The 3 most recent lava flows filled the channel 10-75 m deep and flowed up to 26 kilometers downvalley, creating long, low dams that were subject to gradual, rather than catastrophic, removal. In the last 125 ka, the Saddle Butte and West Crater lava dams created reservoirs into which 10-30 meters of silt and sand were deposited. The river overtopped the dams and in most reaches eventually cut a new channel through the adjacent, less resistant bedrock buttresses. Terraces at several elevations downstream and upstream of the West Crater dam indicate periods of episodic incision ranging from 0.28 to 1.7 mm/yr., based on 3He exposure ages on strath surfaces and boulder-rich fluvial deposits. In contrast to the lava dams, outburst flood deposits associated with landslide dams are common along the river. The mechanisms of failure are related to the geologic setting, and include rotational slump complexes, cantilevered blocks and block slides, and massive earthflows. Most large-scale mass movements occur in reaches where the Owyhee canyon incises through stacks of interbedded fluviolacustrine sediments capped with lava flows. The frequently observed association of landslides and flood

The work will present an ongoing national Project that have as final goal to provide the local emergency services with warnings of a potential dam failure and ensuing flood as a result of a large earthquake occurrence, allowing further public training for evacuation. Probabilistic seismic hazard (PSH), vulnerability and risk studies in 6 counties from Moldova region including Izvorul Muntelui Dam, down on Bistrita and following on Siret River and theirs affluent will be accomplished during the project. A number of 5 large dams (the most vulnerable) will be studied in detail and flooding maps will be drawn to find the most exposed downstream localities both for risk assessment studies and warnings. The results will consist in local and regional seismic information, dams specific characteristics and locations, seismic hazard maps and risk classes, for all dams sites (for more than 30 dams), inundation maps (for the most vulnerable 5 dams from the region) and possible affected localities. The maps will provide the best available estimate of the general location and extent of dam failure inundation areas and will tell if a specific location lies within a dam failure inundation zone. Besides periodical technical inspections, the monitoring and the surveillance of dams' related structures and infrastructures, there are some more seismic specific requirements towards dams' safety. The most important one is the seismic risk assessment that can be accomplished by rating the dams into seismic risk classes using the theory of Bureau and Ballentine (2002), and Bureau (2003), taking into account the maximum expected peak ground motions at the dams site. In this paper we will obtain the ground motion parameters in the dams locations using probabilistic hazard assessment techniques, the structures vulnerability and the downstream risk characteristics (human, economical, historic and cultural heritage, etc) in the areas that might be flooded in the case of a dam failure, and will

Dam removal has been widely viewed as an important river restoration strategy and an interesting scientific opportunity, the latter because it represents a real-time, full-scale field experiment on fluvial adjustment. Removals therefore offer an excellent setting for testing analytical models of sediment transport, morphologic change, and our capacity to predict short- and medium-term channel evolution in response to changing water and sediment transport regimes. Most dam removals to date have involved relatively small structures and modest releases of sediment stored in pre-removal reservoirs. The largest instantaneous and uncontrolled release of sediment accompanying a dam removal occurred with the breaching of the Marmot coffer dam on the Sandy River in Oregon in October 2007. Marmot Dam was a 14-m-high by 50-m-wide diversion dam built in 1913 as part of a larger hydroelectric project. It was located on the Sandy River, an energetic gravel to cobble-bed river that naturally carries copious quantities of sand and gravel, ~45 km upstream from its confluence with the Columbia River near Portland, Oregon. At the time of removal, the reservoir upstream of the dam was completely filled with ~750,000 m3 of sand (40%) and gravel (60%). The river below the dam includes bedrock gorges, mixed bedrock/alluvial reaches, and alluvial reaches with well-developed gravel and sand bars. The decision to remove the dam was motivated by a combination of increasing maintenance costs and an unfavorable future economic return due to the necessity of installing expensive fish passage facilities to meet relicensing requirements. Portland General Electric, the dam's owner, surrendered the dam's license in 1999, and removal commenced in summer 2007. To remove the concrete structure, a temporary coffer dam was constructed 70 m upstream. In October 2007 the coffer dam was breached and the river allowed to erode the remaining impounded sediment (~730,000 m3). Physical modeling conducted at

The Aswan High Dam, 2.5 miles across and 364 feet high, (24.0N, 33.0E) completed in 1971, was constructed to supply cheap hydroelectric power to both Egypt and Sudan by impounding, controling and regulating the flood waters of the Nile River in Lake Nasser, the world's second largest artifical lake. The lake extends over 500 miles in length, covers an area of some 2,000 square miles and is as much as 350 feet deep at the face of the dam.

... 33 Navigation and Navigable Waters 3 2012-07-01 2012-07-01 false Mississippi River at Keokuk, Iowa; operation of power dam by Mississippi River Power Co. 207.310 Section 207.310 Navigation and Navigable... Mississippi River at Keokuk, Iowa; operation of power dam by Mississippi River Power Co. (a) All...

"Watershed development" has been the dominant paradigm for water management in India for the last two decades. Current spending on watershed development programmes rivals spending on large dams. In practice, watershed development involves a range of soil and water conservation measures including building check dams, gully plugs, contour bunds etc. Despite their dominance in water management paradigms, relatively little empirical data exists on these structures. Importantly, even though the benefits of individual watershed structures are recognized, the cumulative impact of building hundreds of such structures on hydrologic partitioning of a watershed remains unknown. We investigated the role of check dams in two small milli-watersheds in the Arkavathy River basin in South India. We conducted a comprehensive census of all check dams in the two milli-watersheds with a total area of 26 sq km. 40 check dams (representing a density of 1.35/sq km of watershed area) were geotagged, photographed, measured and their condition was recorded. We then selected twelve check dams and monitored the water stored using capacitance sensors. We also set up Automatic Weather Stations in each watershed. Inflows, evaporation and infiltration were calculated at each site to evaluate how check dams alter hydrologic partitioning in the watershed as a whole.

of dense floodplain vegetation, consisting primarily of native cottonwood and willow and non-native tamarisk shrubs. Moderate flood releases (~7000 ft3/s) from Alamo Dam in the early 1990's widened the river channel and resulted in the establishment of new woody vegetation. For the following nine years, relatively steady, low discharges were released from the dam, resulting in channel narrowing, extensive beaver pond creation, and dense vegetation growth. Moderate flood releases in 2005 again widened channels, destroyed beaver ponds, and created conditions suitable for new vegetation establishment. In addition to understanding the specific conditions along the Bill Williams River, our work should contribute to a more general understanding of connections between fluvial processes and floodplain vegetation, in the contexts of geomorphic response downstream of a large dam and efforts to manage streamflow for ecological benefits downstream.

The Klamath River is a major river in northern California and southern Oregon. Iron Gate Dam divides the river into the two subunits where there is a significant change in utilization of the river. Downstream of Iron Gate Dam, the river is very important for the propagation of salmon. To address concerns relating to substrate conditions in the mainstem Klamath River below Iron Gate Dam, the Arcata, California, office of the U.S. Fish and Wildlife Service contracted with the U.S. Geological Survey (USGS) to determine flushing flows required to improve and maintain quality spawning and rearing habitats for salmon, and to reduce the abundance of preferred habitats of the polychaete worm suspected of being the intermediate host for Ceratomyxa shasta, a species of bacteria that infects fish. Historically, the river has had the capacity to move sediment just below Iron Gate Reservoir, but there have been periods when the capacity was very low. The results indicate that if the future is more like the pre-1961 period (low transport capacity) than the more recent period, there will be significant sediment issues in the Klamath River below Iron Gate Dam. It seems that during normal or wet years, winter months, and periods of high flow, sediments are flushed either downstream or deposited on higher surfaces. The recent drought conditions during 2000-2005 probably resulted in extensive fine-grained sedimentation along the river, which in turn may have caused increased establishment of aquatic vegetation and increased concentrations of C. shasta. It appears that releases from Iron Gate Dam as far downstream as Seiad Valley are important in maintaining flow conditions to flush the fines and clean the gravels in the river during summer months, or during drought years. Sediment transport studies indicate that supplemental flows during dry or drought conditions may provide some flushing flows in reaches downstream of the dam. For purposes of flushing fine sediments during drought

The Elwha dam removal project presents an ideal opportunity to study how historic reduction and subsequent restoration of sediment supply alter river-floodplain dynamics in a large, forested river floodplain. We used remote sensing and onsite data collection to establish a historical record of floodplain dynamics and a baseline of current conditions. Analysis was based on four river reaches, three from the Elwha River and the fourth from the East Fork of the Quinault River. We found that the percentage of floodplain surfaces between 25 and 75 years old decreased and the percentage of surfaces >75 years increased in reaches below the Elwha dams. We also found that particle size decreased as downstream distance from dams increased. This trend was evident in both mainstem and side channels. Previous studies have found that removal of the two Elwha dams will initially release fine sediment stored in the reservoirs, then in subsequent decades gravel bed load supply will increase and gradually return to natural levels, aggrading river beds up to 1 m in some areas. We predict the release of fine sediments will initially create bi-modal grain size distributions in reaches downstream of the dams, and eventual recovery of natural sediment supply will significantly increase lateral channel migration and erosion of floodplain surfaces, gradually shifting floodplain age distributions towards younger age classes.

The aim of this study was to determine if Arase dam gate removal and flushing elevated concentrations of any trace elements in Kuma River and Yatsushiro Bay sediments or caused riverine environmental change. The Arase dam gate on the Kuma River was opened in April 2010. Surface and bottom sediments were compared using 10-cm-long cores (2011) and two grain size fractions. Surface sediment data from 2002, 2012, and 2013 from the Kuma River and Yatsushiro Bay were also compared. The sediments were analyzed using XRF for 23 elements, and the grain size analysis was done. The short core surface and bottom sediments do not show major chemical changes, and therefore, may not represent post-and pre-dam sediments. Results based on 2011 samples show that the removal of the Arase dam gates in 2010 has been geoenvironmentally beneficial due to the decrease of environmentally related trace elements Pb and Zn in 2013. However, a slight increase in the levels of Cr, Cu, Zr, and Nb in 2013 indicates that periodic flushing in winter leads to elevation in these elements due to an increase in the fine fraction. Metal enrichment factors (EF) in 2002 are higher and these have decreased by 2013. Some elements exceed environmental guidelines, but this is due to natural background values, and there is no anthropogenic contamination. Thus, the environment of the river and bay has been significantly improved due to the dam opening. This result suggests that assessment and environmental monitoring studies are very important for dam management and future decision making. PMID:25182684

Chiloquin Dam was constructed in 1914 on the Sprague River near the town of Chiloquin, Oregon. The dam was identified as a barrier that potentially inhibited or prevented the upstream spawning migrations and other movements of endangered Lost River (Deltistes luxatusChasmistes brevirostris) suckers, as well as other fish species. In 2002, the Bureau of Reclamation led a working group that examined several alternatives to improve fish passage at Chiloquin Dam. Ultimately it was decided that dam removal was the best alternative and the dam was removed in the summer of 2008. The U.S. Geological Survey conducted a long-term study on the spawning ecology of Lost River, shortnose, and Klamath largescale suckers (Catostomus snyderi) in the Sprague and lower Williamson Rivers from 2004 to 2010. The objective of this study was to evaluate shifts in spawning distribution following the removal of Chiloquin Dam. Radio telemetry was used in conjunction with larval production data and detections of fish tagged with passive integrated transponders (PIT tags) to evaluate whether dam removal resulted in increased utilization of spawning habitat farther upstream in the Sprague River. Increased densities of drifting larvae were observed at a site in the lower Williamson River after the dam was removed, but no substantial changes occurred upstream of the former dam site. Adult spawning migrations primarily were influenced by water temperature and did not change with the removal of the dam. Emigration of larvae consistently occurred about 3-4 weeks after adults migrated into a section of river. Detections of PIT-tagged fish showed increases in the numbers of all three suckers that migrated upstream of the dam site following removal, but the increases for Lost River and shortnose suckers were relatively small compared to the total number of fish that made a spawning migration in a given season. Increases for Klamath largescale suckers were more substantial. Post-dam removal monitoring

..., Nevada, from the Pioneer Hotel to the Edgewater Hotel. Laughlin Aquamoto Sports Challenge and Expo.... PDT. Where: That portion of the Colorado River near Laughlin, Nevada, from Davis Dam to Harrah's...

..., Nevada, from the Pioneer Hotel to the Edgewater Hotel. Laughlin Aquamoto Sports Challenge and Expo.... PDT. Where: That portion of the Colorado River near Laughlin, Nevada, from Davis Dam to Harrah's...

Dam construction and its impact on downstream fluvial processes may substantially alter ambient bank stability and erosion. Three high dams (completed between 1953 and 1963) were built along the Piedmont portion of the Roanoke River, North Carolina; just downstream the lower part of the river flows across largely unconsolidated Coastal Plain deposits. To document bank erosion rates along the lower Roanoke River, >700 bank-erosion pins were installed along 66 bank transects. Additionally, discrete measurements of channel bathymetry, turbidity, and presence or absence of mass wasting were documented along the entire study reach (153 km). A bank-erosion- floodplain-deposition sediment budget was estimated for the lower river. Bank toe erosion related to consistently high low-flow stages may play a large role in increased mid- and upper-bank erosion. Present bank-erosion rates are relatively high and are greatest along the middle reaches (mean 63 mm/yr) and on lower parts of the bank on all reaches. Erosion rates were likely higher along upstream reaches than present erosion rates, such that erosion-rate maxima have since migrated downstream. Mass wasting and turbidity also peak along the middle reaches; floodplain sedimentation systematically increases downstream in the study reach. The lower Roanoke River isnet depositional (on floodplain) with a surplus of ??2,800,000 m3yr. Results suggest that unmeasured erosion, particularly mass wasting, may partly explain this surplus and should be part of sediment budgets downstream of dams. ?? 2009 The Geological Society of America.

surveys of diadromous and resident fish as well as benthic macroinvertebrates. Here we report the results of nearly three years of physical and biological data collection since the Simkins Dam removal. Our physical monitoring results largely comport with pre-removal modeling estimates and earlier data from a northeast U.S. dam removal site with many geomorphic similarities. Incision and evacuation of a substantial proportion of the sediments impounded by the Simkins dam happened rapidly during a period of relatively moderate flows, aggrading the reach immediately downstream and the upper portion of the Bloede impoundment by as much as 1.5 meters. Removal of the remaining impounded sediments, and remobilization of the initial aggradation between the Simkins Dam site and the Bloede impoundment, was substantially complete by April, 2012, accomplished by moderate discharges and episodic floods. Tropical Storm Lee, an estimated 10-year event in September, 2011, was particularly important for advancing the sediment pulse downstream of Bloede Dam where a modest, but persistent, veneer of Simkins sediment is found today as far as 7 km downstream. Though diadromous and resident fish response is neither as rapid nor as conclusive as the physical response, we find that benthic fish and macroinvertebrates respond quickly in river reaches affected by dam removal in expected ways.

After years of anticipation, volumes of Environmental Impact Statements, unprecedented mitigation projects, and the multifaceted collection of pre-dam removal data, the deconstruction phase of the Elwha River restoration project officially began on September 17th, 2011. With their simultaneous decommissioning, the removal of the 64 m tall Glines Canyon Dam and 33 m tall Elwha Dam represents one of the largest such projects of its kind in North America. The nearly 19 million m3 of sediment residing in the dammed reservoirs is being eroded by the river in one of the largest controlled releases of sediment into a river and marine waters in recorded history. The release of sediment and the halting of deconstruction and reservoir draw down activities during "fish windows" are largely determining a deconstruction schedule expected to last about 2 years. High suspended sediment concentrations, modeled to exceed 10,000 mg/L during the highest flows and to exceed 500 mg/L for 39% of the time in year 4 of the project (15% is the recorded background level entering the upper reservoir), could last for up to 3-5 years following dam removal depending on hydrological conditions. Anadromous fish, including three federally listed species (Puget Sound Chinook salmon, steelhead, and bull trout), reside in the river downstream of the Elwha dam for part of their life cycle. All five species of Pacific salmon and steelhead, either locally extirpated (sockeye) or persisting below the impassable Elwha Dam in degraded spawning and rearing habitat, are expected to recolonize the watershed to degrees that will vary spatially and temporally due to life history characteristics and levels of human intervention. During the first year of dam removal, adult coho salmon and steelhead were relocated from areas of high turbidity downstream of the Elwha Dam site to two tributaries upstream, where some of them successfully spawned. Additionally, steelhead were observed to naturally migrate past the

This paper investigates post-dam geomorphic and vegetation changes in the Sauce Grande River, a meandering dryland river impounded by a large water-conservation dam. As the dam impounds a river section with scarce influence of tributaries, sources for fresh water and sediment downstream are limited. Changes were inspected based on (i) analysis of historical photographs/imagery spanning pre- (1961) and post-dam (1981, 2004) channel conditions for two river segments located above and below the dam, and (ii) field survey of present channel conditions for a set of eight reference reaches along the river segments. Whilst the unregulated river exhibited active lateral migration with consequent adjustments of the channel shape and size, the river section below the dam was characterized by (i) marked planform stability (93 to 97%), and by (ii) vegetation encroachment leading to alternating yet localized contraction of the channel width (up to 30%). The present river displays a moribund, stable channel where (i) redistribution of sediment along the river course no longer occurs and (ii) channel forms constitute a remnant of a fluvial environment created before closing the dam, under conditions of higher energy. In addition to providing new information on the complex geomorphic response of dryland rivers to impoundment, this paper represents the very first geomorphic assessment of the regulated Sauce Grande and therefore provides an important platform to underpin further research assessing the geomorphic state of this highly regulated dryland river.

The impending removal of two dams on the Elwha River in Washington State offers a unique opportunity to study ecosystem restoration at a watershed scale. We examine how periphyton and benthic invertebrate assemblages vary across regulated and unregulated sections of the Elwha River and across different habitat types, and establish baseline data for tracking future changes following dam removal. We collected multiple years of data on physical habitat, water chemistry, periphyton, and benthic invertebrates from 52 sites on the Elwha River and a reference section on the Quinault River, a neighboring basin. We found that substrate in regulated river sections was coarser and less heterogeneous in size than in unregulated sections, and summer water temperature and specific conductivity higher. Periphyton biomass was also consistently higher in regulated than unregulated sections. Benthic invertebrate assemblage structure at sites above both dams was distinct from sites between and below the dams, due in large part to dominance of mayfly taxa compared to higher relative abundance of midges and non-insect taxa at downstream sites. Following dam removal, we anticipate that both periphyton and benthic invertebrate abundance and diversity will temporarily decrease between and below dams as a result of sediment released from behind the reservoirs. Over the long-term, increased floodplain heterogeneity and recolonization by anadromous fish will alter benthic invertebrate and periphyton assemblages via increases in niche diversity and inputs of marine-derived nutrients. The extended timeline predicted for Elwha River recovery and the complexities of forecasting ecological response highlights the need for more long-term assessments of dam removal and river restoration practices.

Subcommittee on Sedimentation: Sediment Management and Dam Removal Workshop; Portland, Oregon, 14-16 October 2008; For a host of reasons including dam safety, maintenance costs, and ecological concerns, more dams are currently being removed each year in the United States than are being constructed. Because many reservoirs have accumulated sediments within their pools, dam removal can potentially impose a variety of sediment-related risks, including downstream effects on habitat, water quality, infrastructure, and flood storage. Sediment-related risks are particularly heightened when the sediment stored behind a dam is contaminated. Currently no standard procedure exists for assessing sediment-related risks associated with dam removal. As a result, there are wide-ranging levels of analysis used to predict and monitor sediment impacts after a dam is removed. To develop a decision framework for assessing sediment-related effects from dam removals, the U.S. Federal Subcommittee on Sedimentation (SOS) held a workshop in October on the campus of Portland State University, in Oregon, hosted by the U.S. Geological Survey's (USGS) Oregon Water Science Center. At the meeting, attendees crafted a decision framework that will help standardize data collection and analysis methods necessary for understanding sediment-related effects associated with dam removals.

This study evaluated adult steelhead (Oncorhynchus mykiss; fallbacks and kelts) downstream passage at The Dalles Dam in the Columbia River, USA, during the late fall, winter, and early spring months between 2008 and 2011. The purpose of the study was to determine the efficacy of operating the dam’s ice-and-trash sluiceway during non-spill months to provide a relatively safe, non-turbine, surface outlet for overwintering steelhead fallbacks and downstream migrating steelhead kelts. We applied the fixed-location hydroacoustic technique to estimate fish passage rates at the sluiceway and turbines of the dam. The spillway was closed during our sampling periods, which generally occurred in late fall, winter, and early spring. The sluiceway was highly used by adult steelhead (91–99% of total fish sampled passing the dam) during all sampling periods. Turbine passage was low when the sluiceway was not operated. This implies that lack of a sluiceway route did not result in increased turbine passage. However, when the sluiceway was open, adult steelhead used it to pass through the dam. The sluiceway may be operated during late fall, winter, and early spring to provide an optimal, non-turbine route for adult steelhead (fallbacks and kelts) downstream passage at The Dalles Dam.

... RiverDam Removal and Floodplain Restoration Ecosystem Service Valuation Pilot Project AGENCY: National... Elwha RiverDam Removal and Floodplain Restoration Ecosystem Service Valuation Survey it has developed... U.S. history. This project, along with restoration actions planned for the floodplain and...

... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF AGRICULTURE Natural Resources Conservation Service South River Watershed Dam No. 10A, Augusta County, VA AGENCY... not being prepared for the rehabilitation of South River Watershed Dam No. 10A, Augusta...

...: Whitman RiverDam, Inc. e. Name of Project: Crocker Pond Project. f. Location: The project would be located at the existing Crocker Pond Dam, on the Whitman River, in Worcester County, Massachusetts....

The Secor Dam was a low-head weir on an urbanized river that was constructed in 1928 and removed in 2007 for a variety of reasons: (1) it was obsolete and a potential liability to the owner, (2) removal would enhance aquatic ecosystems and fisheries, and (3) removal would improve downstream water quality and help restore downstream sediment budgets. In sum, it was a “river restoration” effort in an urbanized river corridor, with extensive public involvement. Detailed pre- and post-dam removal studies included field sedimentological methods such as trenching and sediment coring. Historical documents assisted in locating the pre-1928 channel and documented that urbanization of this region post-1928 resulted in channel armoring. Detailed channel surveys showed that the result of the dam removal was initial incision and channel widening in the former reservoir, as expected. However, nickzone migration upstream stalled on an exhumed woody peat layer. Studies subsequently showed that this was a hydromorphic paleosol that developed during pre-land clearance times that was buried beneath 2.5-m of anthropogenic or legacy sediments, much of that deposited since about 1950. Today, the river flows through an incised channel between fill-terraces comprised of legacy sediments. Additional coring and survey work documented that the channel lateral migration rates averaged 0.32 m/yr over the past approximately 80 years, and that the meander wavelength appears to be changing in response to dam removal. Public hearings about “river restoration” made it clear that the public has a vision of a restored river that in fact never existed. Significant channel bank erosion and lateral channel migration should be expected until such time as the river system reworks and removes accumulated legacy sediments currently in intrabasinal storage. This finding has important implications in an urbanized setting, where bank erosion is perceived to be a threat to infrastructure and property

Presently, the water discharge rate to the Black Sea by Turkish rivers is approximately 41 km[sup 3]/yr. The sediment discharge rate of Turkish rivers to the Black Sea is 28 x 10[sup 6] t/yr. Before construction of the hydroelectric dams, the sediment discharge rate was approximately 70 x 10[sup 6] t/yr. The sharp reduction in sediment load is largely a result of the dams near the mouths of the Yesil Irmak and Kizil Irmak rivers. Before the construction of dams, Turkish rivers contributed approximately one third of the total amount of sediment received by the Black Sea from all surrounding rivers. The life-span of the major reservoirs varies from approximately only one century (Yesil Irmak river reservoirs) to several thousand years (Sakarya river reservoirs). Life-span for the large Altinkaya Dam reservoir is estimated with approximately 500 yr.

We evaluated Renibacterium salmoninarum infection in smolts of hatchery and wild spring-summer chinook salmon Oncorhynchus tshawytscha sampled during most of the out-migration at Little Goose (1988) and Lower Granite dams (1988-1991) on the Snake River and at Priest Rapids and McNary dams on the Columbia River (1988-1990). We sampled 860-2,178 fish per dam each year. Homogenates of kidney-spleen tissue from all fish were tested for the presence of R. salmoninarum antigens by the enzyme-linked immunosorbent assay (ELISA), and homogenates from 10% of the fish were examined by the fluorescent antibody technique (FAT). Although only 1-11% of fish sampled at a given dam during any 1 year exhibited lesions characteristic of bacterial kidney disease, 86-100% of the fish tested positive for R. salmoninarum antigen by ELISA, whereas 4-17% of the fish tested positive by the FAT. During most years, a majority (68-87%) of fish testing positive by the ELISA had low R. salmoninarum antigen levels, but in 1989, 53% of positive fish from Lower Granite Dam and 52% from McNary Dam showed medium-to-high antigen levels. For most years, the highest mean antigen levels were measured in fish sampled after 75% of the total out-migrants had passed a given dam. When the largest numbers of fish were being collected for bypass or downriver transportation, mean antigen levels were relatively low.

The hydrologic regime of the Illinois River has been altered over the past 100 years. Locks and dams regulate water surface elevations and flow, enabling commercial navigation to continue year round. This study relates changes in water surface elevation to fish abundance in the river, and establishes target criteria for operating locks and dams. Using longterm records of daily river stage, we identified ecologically meaningful hydrological parameters for eight gage locations along the Illinois River. Inter-annual variability of a long-term fisheries dataset beginning in 1957 was related to variability in stage, flood and recession duration, frequency, timing, and rate of change of water levels. Reversals in water surface elevation, maximum stage levels, and lenght of the spring flood were the most important parameters influencing abundance of age-zero fishes in annual collections. Smallmouth buffalo (Ictiobus bubalus), black crappie (Pomoxis nigromaculatus), freshwater drum (Aplodinotus grunneins), and white bass (Morone chrysops) were most abundant in samples during years that approximated the natural water level regime. Of the 33 hydrologic parameters evaluated for the entire water year from an Illinois River gage site on La Grange Reach, all except average stage in January and Julian date (JD) of maximum stage had moderate or high hydrologic alteration based on the historical range of variation (RVA). The highest degree of hydrologic alteration was for minimum stage levels (1-day, 3-day, and 7-day), rate-of-rise, and rate-of-fall. Other parameters that have been severely altered were 30-day minimum stage, 90-day maximum stage, and the annual number of water level reversals. Operations of the La Grange and Peoria locks and dams could be modified so water level variability would approximate that of the late 1800s, when fish and wildlife resources were abundant. The water regime could be regulated to maintain navigation and improve conditions for native plants and

Columbia River temperatures and flow rates are collected daily at Priest Rapids Dam and Vernita Bridge. These data are necessary for assessing trends or changes in river conditions downstream of Priest Rapids Dam. In order to analyze this data, Pacific Northwest Laboratory developed a computerized data base using existing US Geological Survey flow and temperature records at Priest Rapids Dam and Vernita Bridge. Daily-averaged temperature and daily flow information on the Columbia River just downstream of Priest Rapids Dam and upstream of river mile 380 were collected and stored in a data base. A newly developed computer model, COLSTAT (Columbia River Statistical Update), used the data base to statistically analyze temperature and flow conditions by computing the frequency of occurrence and duration of selected temperatures and flow rates for the Columbia River. Information regarding the data base is presented, as well as, a description of the COLSTAT model.

The recent work in the Nebraska Sand Hills, just north of the North Platte Valley, has revealed the presence of numerous dune dams--sites where eolian sand has filled Pleistocene paleovalleys and caused the formation of lake basins containing abundant small, interdunal lakes. Although the Platte River is considered the southern margin of the Sand Hills, there is a 1,200 sq km triangular area of large dunes in Lincoln County just south of the South Platte. The authors hypothesize that large dunes migrated southward to fill the North Platte Valley during glacial maximum when both the North and South Platte were dry. As Rocky Mountain snowmelt and Great Plains precipitation increased during deglaciation, a single 65 km-long, 15 km-wide, 50 m-deep lake formed behind the massive dune dam. The tentative chronology suggests that the lake was in existence for at least several thousand years. They have not yet found compelling evidence of catastrophic flooding downstream of the former lake. Evidence of two large Quaternary lakes on the White Nile between Khartoum and Malakal (Sudan) was discovered in the 1960's. Shoreline deposits indicate the lakes were 400--600 km long and up to 50 km wide. Although the lakes have been attributed to repeated blockage of the White Nile by clay-rich Blue Nile deposits, the distribution and age of dune sand near the confluence of these rivers suggest that, as in the Nebraska example, the course of the White Nile was blocked by dunes when the region was desiccated in the Late Pleistocene. Lakes behind permeable dams rise to a level where input equals output. Earthen dams are vulnerable to overtopping and piping. The relatively high permeability of dune sand prevents or delays overtopping, and piping is prevented by the extremely high low hydraulic gradients that typify extant sand dams.

Beaver convert lotic stream habitat to lentic through dam construction, and the process is reversed when a flood or other event causes dam failure. We investigated both processes on a regulated Sonoran Desert stream, using the criterion that average current velocity is < 0.2 m s-1 in a lentic reach. We estimated temporal change in the lotic:lentic stream length ratio by relating beaver pond length (determined by the upstream lentic-lotic boundary position) to dam size, and coupling that to the dam-size frequency distribution and repeated censuses of dams along the 58-km river. The ratio fell from 19:1 when no beaver dams were present to < 3:1 after 7 years of flows favourable for beaver. We investigated the dam failure-flood intensity relationship in three independent trials (experimental floods) featuring peak discharge ranging from 37 to 65 m3 s-1. Major damage (breach ??? 3-m wide) occurred at ??? 20% of monitored dams (n = 7-86) and a similar or higher proportion was moderately damaged. We detected neither a relationship between dam size and damage level nor a flood discharge threshold for initiating major damage. Dam constituent materials appeared to control the probability of major damage at low (attenuated) flood magnitude. We conclude that environmental flows prescribed to sustain desert riparian forest will also reduce beaver-created lentic habitat in a non-linear manner determined by both beaver dam and flood attributes. Consideration of both desirable and undesirable consequences of ecological engineering by beaver is important when optimizing environmental flows to meet ecological and socioeconomic goals. ?? 2010 John Wiley & Sons, Ltd.

Dam removal has become an important aspect of river restoration in recent years, but studies documenting the physical and ecological response to dam removal are still lacking - particularly in mountain rivers and following major floods. This presentation documents the recent removal of a large dam on a coarse-grained, steep (an order of magnitude greater than on the Marmot) mountain channel in Taiwan. The Chijiawan river, a tributary of the Tachia River draining a 1236 km2 watershed, is the only habitat in Taiwan of the endangered Formosan landlocked salmon. The habitat of this fish has been cut significantly since the 1960s following construction of check dams designed to prevent reservoir sedimentation downstream. The largest and lowermost barrier on Chijiawan creek is the 15m high, "No. 1 Check Dam" built in 1971. Forty years later, in early 2011, the sediment wedge behind the dam had reached an estimated 0.2 million m3 and the dam toe had been scoured about 4m below its foundation, posing a serious risk of dam failure. For these reasons, the Shei-Pa National Park removed the dam in late May 2011. To monitor the response of the river to dam removal, we installed video cameras, time-lapse cameras, stage recorders, and turbidity sensors, conducted surveys of grain size distributions and longitudinal profiles, and carried out repeat photography. Channel changes were greatest immediately following removal as a result of the high stream power, steep energy slope, and unconsolidated alluvial fill behind the dam. Headcut propagation caused immediate removal of the sand-grade sediment and progressive channel widening. One month after dam removal, a minor flood event excavated a big wedge of sediment from the impoundment. Most of the subsequent downstream deposition occurred within 500m of the dam, with alluviation reaching up to 0.5m in places. Two months after dam removal, erosion had propagated 300m upstream into the impounded sediment along a bed profile of gradient

Existing ice and trash sluiceways are commonly used to pass juvenile salmonids downstream at hydropower dams through a benign, non-turbine route. At The Dalles Dam on the Columbia River, managers undertook optimizing operations of sluiceway weirs to maximize survival of juvenile salmonids at the powerhouse. We applied fixed-location hydroacoustic methods to compare fish passage rates and sluiceway efficiencies for two weir configurations during 2004 and 2005: three weirs versus six weirs, located at the mid- versus east powerhouse, respectively. We also analyzed horizontal distributions of passage at the sluiceway and turbines and the effects of operating turbines beneath open sluiceway gates to provide supporting data relevant to operations optimization. Based on the findings, we recommend the following for long-term operations for the sluiceway at The Dalles Dam: open six rather than three sluiceway weirs to take advantage of the maximum hydraulic capacity of the sluiceway; open the three weirs above the western-most operating main turbine unit (MU) and the three weirs at MU 8 where turbine passage rates are relatively high; operate the turbine units below open sluiceway weirs as a standard procedure; operate the sluiceway 24 h/d year-round to maximize its benefits to juvenile salmonids; and use the same operations for spring and summer emigrants. These operational concepts are transferable to dams where sluiceway surface flow outlets are used protect downstream migrating fishes.

Two dams on the Elwha River, Washington State, USA trapped over 25 million m3 of mud, sand, and gravel since the early 1900s and contributed to erosion of the delta protruding into the Strait of Juan de Fuca. The removal of the Elwha and Glines Canyon dams, initiated in September 2011, is providing an unprecedented opportunity to examine the geomorphic response of a coastal delta to massive changes in river sediment supply. Observations once or twice a year prior to and during dam removal of nearshore bathymetry, collected using personal watercraft equipped with RTK GPS and single-beam echosounders and beach topography, collected with RTK GPS mounted on backpacks provide a sequence of continuous DEM surfaces to quantify geomorphic change. Bed sediments are sampled by grab sampler in water depths between -9 and -1 m around the delta, and by hand and a 'cobble-cam' digital camera during low tide on sub-aerial beaches. An approximately monthly series of low altitude, high-resolution vertical aerial ortho-images qualitatively document sub-aerial changes in coastal landforms. Comparison of the March 2013 survey with surveys conducted prior to dam removal shows large changes in the morphology of the river mouth and submarine delta. Sediment accumulation was widespread throughout the survey area but was concentrated primarily in two distinct areas. The largest area of deposition was located adjacent to the river mouth and covered approximately 368,000 m2 with an average thickness of 3.1 m and a maximum of 8 m. A secondary area of deposition was observed to the east of the river mouth and covered 115,600 m2 with a mean thickness of 0.69 m and a maximum of 1.8 m. Net accumulation within the study area totals roughly 1,300,000 m3 since the removal of the two dams began in 2011. Surface sediment of the primary deposit adjacent to the river mouth is coarser (coarse to medium sand) than the secondary deposit to the east (medium to fine sand). Numerical model simulations of

Flooding, and the resulting economic damage to roads and property, is associated with natural dams such as beaver dams or log jams. For this reason, humans often remove natural dams; however, river reaches with natural dams provide very different ecosystem services in comparison with free-flowing river reaches. Therefore, the goal of this project is to assess the differences in ecosystem state between these different river reach types in the northeastern United States. We focused on differences in basic chemistry (e.g., dissolved oxygen, pH, temperature, and organic carbon) to assess the impact of natural dams on river ecosystem state. Study sites include rivers in the White Mountains and southeastern New Hampshire at locations with beaver dams, beaver ponds, beaver meadows, log jams, and free-flowing reaches. Dissolved oxygen, ORP, pH, temperature, and conductivity were measured in the field with a YSI Professional Plus meter. Water samples were collected for subsequent laboratory analysis of total organic carbon with a Shimadzu TOC-L. Preliminary results show that the chemistry of river water varies with feature type. Most significantly, dissolved oxygen concentrations are highest in free-flowing reaches and lowest in beaver ponds. Although beaver ponds are often associated with lower pH, due the increased concentration of organic acids, some beaver ponds can increase pH when compared to free-flowing reaches on the same river. Early results also show that water chemistry returns quickly to the chemistry typical of the free-flowing river reaches after being altered by a natural dam. Overall, natural dams create a river system that has more heterogeneity, and therefore has opportunities to provide more ecosystem functions, than a purely free-flowing river; this can increase the number of supported instream and riparian species. By increasing the understanding of how natural dams affect the chemistry of river water, river engineers can improve their decisions on how

Recently, there have been discussions of the relative merits of passage of fishes around hydroelectric dams on three rivers (Au Sable, Manistee, and Muskegon) in Michigan. A hazard assessment was conducted to determine the potential for adverse effects on bald eagles that could consume such fishes from above and below dams on the three primary rivers. The hazard assessments were verified by comparing the reproductive productivities of eagles nesting in areas where they ate primarily fish from either above or below dams on the three primary rivers, as well as on two additional rivers in Michigan, the Menominee and Thunder Bay. Concentrations of organochlorine insecticides (OCI), polychlorinated biphenyls (total PCBs), 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQ), and total mercury (Hg) were measured in composite samples of fishes from above and below hydroelectric dams on the Manistee and Muskegon Rivers, which flow into Lake Michigan, and the Au Sable River, which flows into Lake Huron. Mean concentrations of OCI, total PCBs, and TCDD-EQ were all greater in fishes from below the dams than in those from above. The hazard assessment indicated that current concentrations of Hg and OCI other than DDT (DDT+DDE+DDD) in fish from neither above nor below dams would present a significant hazard to bald eagles (Haliaeetus leucocephalus). Both total PCBs and TCDD-EQ in fishes from below the dams currently present a significant hazard to bald eagles, since their mean hazard quotients (HQ) were all greater than one. PMID:7487154

This paper provides a scientific approach to eco-design of river fishways to allow upstream movement of fish past new and existing dams in China. This eco-design approach integrates principles of fish ecology/behavior and engineering, a scientific field also known as bio-engineering or eco-hydraulics. We define a fishway as a structure or mechanism to convey fish upstream past a dam. Man-made or natural stream beds can be part of the fishway mechanism. Fish include bony and non-bony fishes, and upstream passage is the concern here, not downstream passage. The problem is dams block access to upstream habitat used for spawning, rearing, and refuge, i.e., dams decrease habitat connectivity. A solution to alleviate this problem is to design fishways, preferably while the dam is being designed, but if necessary, as retrofits afterward to provide a route that fish can and will use to pass safely upstream without undue delay. Our eco-design approach for fishways involves eight steps: 1) identify the primary species of importance; 2) understand basic ecology and behavior of these fish; 3) characterize the environmental conditions where passage is or will be blocked; 4 identify fishway alternatives and select a preferred alternative; 5) establish eco-design criteria for the fishway, either from management agencies or, if necessary, developed specifically for the given site; 6) where needed, identify and perform research required to resolve critical uncertainties and finalize the eco-design criteria; 7) apply the eco-design criteria and site-specific considerations to design the fishway, involving peer-review by local stakeholders in the process; 8) build the fishway, monitor its effectiveness, and apply the lessons learned. Example fishways are described showing a range of eco-designs depending on the dam site and fish species of concern. We apply the eco-design principles to recommend an approach and next steps for a fishway to pass fish upstream at Hanfeng Dam, an

The large Alqueva dam was built in the early 2000s in the Guadiana River (southern Portugal) and has highly controlled the freshwater flowing into the Guadiana estuary, leading to significant changes in the natural hydrological regime. To evaluate the impacts of water restriction and flow regularization on estuarine phytoplankton and their environmental variables, sampling campaigns were conducted in the Guadiana estuary throughout a 14-year period, covering different phases related to the Alqueva dam construction. Significant alterations in phytoplankton and their environmental drivers were observed. In the post-filling period, river flow became more constant throughout the year and its natural seasonal variability, with maxima in the winter and minima in the summer, was greatly reduced, leading to higher river flows in the summer and lower in the winter, in relation to the pre-filling phase. Nutrient and light availability and, hence, phytoplankton dynamics, were greatly affected. Phytoplankton abundance and biomass decreased in the post-filling phase related to a decrease in diatoms and cyanobacteria. Since cyanobacteria blooms in the Guadiana are frequently dominated by toxic species, this constitutes an improvement in water quality. However, the overall decrease in phytoplankton biomass and, specifically, the decline in diatom biomass, will have major consequences for the higher trophic levels that depend on planktonic food.

The U.S. Geological Survey Forecast Mekong project is providing technical assistance and information to aid management decisions and build science capacity of institutions in the Mekong River Basin. A component of this effort is to produce a synthesis of the effects of dams and other engineering structures on large-river hydrology, sediment transport, geomorphology, ecology, water quality, and deltaic systems. The Mississippi River Basin (MRB) of the United States was used as the backdrop and context for this synthesis because it is a continental scale river system with a total annual water discharge proportional to the Mekong River, has been highly engineered over the past two centuries, and the effects of engineering have been widely studied and documented by scientists and engineers. The MRB is controlled and regulated by dams and river-engineering structures. These modifications have resulted in multiple benefits including navigation, flood control, hydropower, bank stabilization, and recreation. Dams and other river-engineering structures in the MRB have afforded the United States substantial socioeconomic benefits; however, these benefits also have transformed the hydrologic, sediment transport, geomorphic, water-quality, and ecologic characteristics of the river and its delta. Large dams on the middle Missouri River have substantially reduced the magnitude of peak floods, increased base discharges, and reduced the overall variability of intraannual discharges. The extensive system of levees and wing dikes throughout the MRB, although providing protection from intermediate magnitude floods, have reduced overall channel capacity and increased flood stage by up to 4 meters for higher magnitude floods. Prior to major river engineering, the estimated average annual sediment yield of the Mississippi River Basin was approximately 400 million metric tons. The construction of large main-channel reservoirs on the Missouri and Arkansas Rivers, sedimentation in dike

Records of diversion and return flows for water years 1961?2004 along a reach of the Klamath River between Link River and Keno Dams in south-central Oregon were evaluated to determine the cause of a water-balance inconsistency in the hydrologic data. The data indicated that the reach was losing flow in the 1960s and 1970s and gaining flow in the 1980s and 1990s. The absolute mean annual net water-balance difference in flows between the first and second half of the 44-year period (1961-2004) was approximately 103,000 acre-feet per year (acre-ft/yr). The quality of the diversion and return-flow records used in the water balance was evaluated using U.S. Geological Survey (USGS) criteria for accuracy. With the exception of the USGS Klamath River at Keno record, which was rated as 'good' or 'excellent,' the eight other flow records, all from non-USGS flow-measurement sites, were rated as 'poor' by USGS standards due to insufficient data-collection documentation and a lack of direct discharge measurements to verify the rating curves. The record for the Link River site, the most upstream in the study area, included both river and westside power canal flows. Because of rating curve biases, the river flows might have been overestimated by 25,000 acre-ft/yr on average from water years 1961 to 1982 and underestimated by 7,000 acre-ft/yr on average from water years 1983 to 2004. For water years 1984-2004, westside power canal flows might have been underestimated by 11,000 acre-ft/yr. Some diversion and return flows (for mostly agricultural, industrial, and urban use) along the Klamath River study reach, not measured continuously and not included in the water-balance equation, also were evaluated. However, the sum of these diversion and return flows was insufficient to explain the water-balance inconsistency. The possibility that ground-water levels in lands adjacent to the river rose during water years 1961-2004 and caused an increase in ground-water discharge to the river

Three high-flow experiments (HFEs) were conducted by the U.S. Department of the Interior at Glen Canyon Dam, Arizona, in March 1996, November 2004, and March 2008. Also known as artificial or controlled floods, these scheduled releases of water above the dam's powerplant capacity were designed to mimic pre-dam seasonal flooding on the Colorado River. The goal of the HFEs was to determine whether high flows could be used to benefit important downstream resources in Glen Canyon National Recreation Area and Grand Canyon National Park that have been affected by the existence and operation of Glen Canyon Dam. These downstream resources include native fish, particularly endangered humpback chub (Gila cypha), terrestrial and aquatic sandbar habitats, cultural sites, and recreational resources. This Fact Sheet summarizes HFE-related studies published since 1996 and outlines a possible strategy for implementing future HFEs.

... 33 Navigation and Navigable Waters 3 2014-07-01 2014-07-01 false Twin Buttes Dam and Reservoir... and Reservoir, Middle and South Concho Rivers, Tex. The Bureau of Reclamation, or its designated agent, shall operate the Twin Buttes Dam and Reservoir in the interest of flood control as follows:...

Native diadromous fishes have been extirpated from much of the Susquehanna River system for nearly a century. Recent restoration efforts have focused on removal of dams, but there are hundreds of dams and presently there is no biologically based system to assist in prioritizing their removal. We present a new method that uses existing habitat suitability index models (HSI) for American shad Alosa sapidissima, alewife A. pseudoharengus, blueback herring A. aestivalis, and American eel Anguilla rostrata to prioritize the removal of non-hydropower dams within the Susquehanna River system. We ranked HSI scores for each of the four species, association between a landscape-scale factor and HSIs, length of river opened by removing a dam, and distance from the mouth at Chesapeake Bay for each dam and then calculated a mean rank prioritization for dam removal by averaging the ranks for the seven criteria. This prioritization method is resistant to outliers, is not strongly affected by somewhat arbitrary decisions on metrics included in the analysis, and provides a biologically based prioritization for dam removal that can be easily amended to include other metrics or adapted to other river systems and that complements other social and economic considerations that must be included in decisions to remove dams.

... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF HOMELAND SECURITY Coast Guard 33 CFR Part 100 Special Local Regulations; Annual Marine Events on the Colorado River, Between Davis Dam (Bullhead City, Arizona) and Headgate Dam (Parker, Arizona) Within the San Diego...

Water is an essential requirement for human existence. However, due to economic and social developments as well as climate change, both water withdrawals and water supplies are changing significantly. Water consumption has an increasing tendency in all the sectors mainly in agricultural use, industrial and power generation use, and domestic use. The total water demand of US is projected to increase by about 12.3 percent between 2000 and 2050. In the meantime, water supplies are being impacted by climate change and anthropogenic impacts. It has, thus, become a necessity to be able to model and predict the water flow based on integration of spatial elements and atmospheric/climatic changes. The purpose of this project is to model the surface run off in the Yuba River Watershed, California, given the geographic and geomorphologic complexities and the presence of dams that regulate the water discharge. The model used, the Watershed Environmental Hydrology Model, WEHY, utilizes upscaled hydrologic conservation equations to describe the evolution of the hydrologic processes and environmental processes within a watershed in time and space. It is capable of accounting for the effect of heterogeneity within natural watersheds. With the development of modern geographic information system (GIS) and remote sensing technologies, increasingly more watershed physical attributes are digitally available, such as topography, geology, soils, land/vegetation cover, and so on. Because the WEHY model parameters are related to the physical properties of the watershed, it is possible to estimate the geomorphologic parameters and the soil hydraulic parameters of the WEHY model by means of existing GIS data sets that describe the geomorphologic features and the soil conditions. So the geographic and geomorphologic complexities are addressed by WEHY and GIS. Presence of big dams makes it necessary to define operation rules taking care of all the constraints including downstream water demand

In 2008, the National Marine Fisheries Service completed the sixteenth year of a study to estimate survival and travel time of juvenile salmonids Oncorhynchus spp. passing through dams and reservoirs on the Snake and Columbia Rivers. All estimates were derived from detections of fish tagged with passive integrated transponder (PIT) tags. We PIT tagged and released a total of 18,565 hatchery steelhead O. mykiss, 15,991 wild steelhead, and 9,714 wild yearling Chinook salmon O. tshawytscha at Lower Granite Dam in the Snake River. In addition, we utilized fish PIT tagged by other agencies at traps and hatcheries upstream from the hydropower system and at sites within the hydropower system in both the Snake and Columbia Rivers. These included 122,061 yearling Chinook salmon tagged at Lower Granite Dam for evaluation of latent mortality related to passage through Snake Riverdams. PIT-tagged smolts were detected at interrogation facilities at Lower Granite, Little Goose, Lower Monumental, Ice Harbor, McNary, John Day, and Bonneville Dams and in the PIT-tag detector trawl operated in the Columbia River estuary. Survival estimates were calculated using a statistical model for tag-recapture data from single release groups (the single-release model). Primary research objectives in 2008 were to: (1) estimate reach survival and travel time in the Snake and Columbia Rivers throughout the migration period of yearling Chinook salmon and steelhead, (2) evaluate relationships between survival estimates and migration conditions, and (3) evaluate the survival estimation models under prevailing conditions. This report provides reach survival and travel time estimates for 2008 for PIT-tagged yearling Chinook salmon (hatchery and wild), hatchery sockeye salmon O. nerka, hatchery coho salmon O. kisutch, and steelhead (hatchery and wild) in the Snake and Columbia Rivers. Additional details on the methodology and statistical models used are provided in previous reports cited here. Survival

The E.B. Campbell Dam on the Saskatchewan River, east-central Saskatchewan, was constructed in 1962, forming Tobin Lake (2.2 billion m3 capacity), which today impounds most fluvial sediment and disrupts normal outflow patterns. Thirty-five kilometers below the dam, the river diverts into a 500 km2 belt of alluvial sediment initiated by an avulsion ~ 140 years ago, rejoining the parent channel 108 km from the dam. Effects of the dam on channel geomorphology, including the historical channel (reach I) and the more recent avulsion-affected channels, were investigated by pre- and post-dam cross section surveys combined with grain-size and bedload measurements. Twenty-three sites were surveyed at least twice, and 14 were resurveyed annually in 2003-2014 (except 2007) during which significant floods occurred in 2005, 2011, and 2013. All channel cross sections up to 81 km below the dam have coarsened and enlarged since closure, resulting in excavation of 35.4 × 106 m3 of channel-perimeter sediment since 1962. The most proximal segment is armored and has changed little in recent years. Since 2003, channel enlargement has been greatest in the 35-81 km segment between the avulsion site and the Forks (reaches II, III), manifested as widening and deepening. Enlargement rates were greatest during the three floods, and the paucity of bedload has prevented degraded portions of the channel bed from replenishment following flooding. Budget calculations based on bedload measurements and channel cross-section areas suggest that > 30 years would be required to replace the sediment removed between 2003 and 2014, assuming all available bedload remains in the affected reach. Dam effects appear to be absent or uncertain beyond 81 km, a multichanneled region of varied stages of activity (reach IV), recombining and eventually rejoining the parent Saskatchewan River channel at km 108 (reach V). Sediment evacuated from reaches I-III is sufficient to sustain modest aggradation in some distal

Closure of Glen Canyon Dam reduced sand supply to the Colorado River in Grand Canyon National Park by about 94% while its operation has also eroded the park's sandbar habitats. Three controlled floods released from the dam since 1995 suggest that sandbars might be rebuilt and maintained, but only if repeated floods are timed to follow tributary sand deliveries below the dam. Monitoring data show that sandbars are dynamic and that their erosion after bar building is positively related with mean daily discharge and negatively related with tributary sand production after controlled floods. The March 2008 flood affected non-native rainbow trout abundance in the Lees Ferry tailwater, which supports a blue ribbon fishery. Downstream trout dispersal from the tailwater results in negative competitive interactions and predation on endangered humpback chub. Early survival rates of age-0 trout increased more than fourfold following the 2008 flood, and twofold in 2009, relative to prior years (2006-2007). Hatch-date analysis indicated that early survival rates were much higher for cohorts that emerged about 2 months after the 2008 flood relative to cohorts that emerged earlier that year. The 2009 survival data suggest that tailwater habitat improvements persisted for at least a year, but apparently decreased in 2010. Increased early survival rates for trout coincided with the increased availability of higher quality drifting food items after the 2008 flood owing to an increase in midges and black flies, preferred food items of rainbow trout. Repeated floods from the dam might sustainably rebuild and maintain sandbars if released when new tributary sand is available below the tailwater. Spring flooding might also sustain increased trout abundance and benefit the tailwater fishery, but also be a potential risk to humpback chub in Grand Canyon.

Due to complex tectonic and geomorphologic factors, the Tibetan Plateau and its surrounding areas, are particularly prone to landslides. Rivers have deeply cut into bedrock, forming narrow valleys that are especially prone to landslide damming. Numerous landslide damming and subsequent dam breaching events are recorded from the region in historical documents and the geosciece literature; these include events at the Dadu River (1786), Diexi (1933), Tanggudong (1967), Yigong (2000), and Tangjiashan (2008). We report the results of a GIS-based analysis of earthquake-generated landslide dams at Diexi. The Diexi Earthquake (M=7.5) occurred on August 25, 1933 and induced a series of giant landslides along the Min River, some of which blocked the river and formed three large landslide lakes. The landslide dam located furthest downstream breached on October 9, 1933, 45 days after the earthquake. The outburst flood resulted in huge damage to the downstream area killing 2,423 people, one of the most serious landslide-related disasters in China during the 20th Century. In the present work, GIS analysis is applied to the Diexi Landslides, based on a review of historical documents and previous studies, data collected during field work, and remote sensing and SRTM-3 digital terrain data. We attempted to determine the precise locations of the 1933 landslides and measured dam height, cross-section area, and volume of the damming landslides. Due to the lack of topographic data before the 1933 earthquake, data of the landslide lakes, including maximum water elevation and total impounded volume can only be estimated. Using credible water levels and inferred submerged topography we calculate an outburst volume for the 1933 event. Moreover, cross-sections are made for both the damming area and the Min River downstream in order to make a general assessment of the damage due to the subsequent flood. Maximum flood discharge is estimated by regression equations. The two remaining lakes on

A one-dimensional channel evolution simulation model (CCHE1D) is applied to assess morphological changes in a reach of the Sandy River, Oregon, USA, due to the Marmot Dam removal in 2007. Sediment transport model parameters (e.g. sediment transport capacity, bed roughness coefficient) were calibrated using observed bed changes after the dam removal. The validated model is then applied to assess long-term morphological changes in response to a 10-year hydrograph selected from historical storm water records. The long-term assessment of sedimentation gives a reasonable prediction of morphological changes, expanding erosion in reservoir and growing deposition immediately downstream of the dam site. This prediction result can be used for managing and planning river sedimentation after dam removal. A simulation-based optimization model is also applied to determine the optimal sediment release rates during dam-removal that will minimize the morphological changes in the downstream reaches.

The removal of Milltown Dam on the Clark Fork River, Montana, USA, is creating a field-scale experiment on upstream and downstream responses to dam removal and on how gravel-bed rivers respond to sediment pulses. Milltown Dam was removed in 2008, reconnecting the Clark Fork River to its upstream basin in terms of sediment transport and fish passage. This dam removal is especially notable because (1) it is the largest dam removal to date in the United States in terms of the volume of reservoir sediment potentially available for downstream transport (over 3 million m3; 1.7 million m3 are being mechanically removed); and (2) the dam is the downstream end of the largest Superfund site in the United States, the Clark Fork Complex, and reservoir sediments are composed largely of contaminated mine tailings. Data collection on pre- and post-dam removal channel morphology, bed sediment characteristics, and sediment loads are being used to investigate spatial and temporal patterns of sediment transport and deposition associated with this dam removal. In the first several months following breaching of the dam, snowmelt runoff with a 3-year recurrence interval peak caused substantial erosion and downstream transport of metals-laden sediments from Milltown reservoir. Reservoir sediments in the Clark Fork arm of Milltown reservoir eroded at levels far exceeding modeling predictions as a result of both incision to the new base level created by dam removal and bank retreat of over 200 m in reaches upstream of a constructed bypass reach and remediation area. Copper and other metals in these eroded reservoir sediments provide a tracer for identifying whether sediment deposits observed downstream of the dam originated from Milltown reservoir or uncontaminated tributaries and indicate that Milltown sediments have reached over 200 km downstream. Downstream deposition has been greatest along channel margins and in side-channel areas, whereas the transport capacity of the active channel

In the Mekong River watershed, traditional social and industrial systems have long existed in harmony with water and biological resources. Since the 1950s, many dam-construction projects have been started to develop power and water resources to meet increasing demand for energy and food production. Since the 1970s, there have been temporary interruptions to these projects because of civil war or regional volatility of international relations. Many of these projects have been restarted in the last 15 years. This raises international interest, as there are transboundary issues cross-border issues related to both development assistance and environmental conservation. By 2008, two Chinese dams had already been completed (the Manwan dam in 1996 and the Dachaoshan dam in 2003) on the Mekong River in Yunnan province. Dam construction has some positive impacts, such as electricity production, management of water resources, and flood control. However, upstream control of water discharge can have negative impacts on traditional agricultural systems and fisheries downstream from the dams, such as drastic changes in flow volume and sediment load. We used hydrological simulation of the watershed to quantify the impact of the construction of the Dachaoshan dam by comparing annual water discharge and sediment transport before and after the dam was completed. Our main objectives were to use watershed hydrologic modeling to simulate changes to annual hydrological parameters and sediment transport, and to map spatio-temporal changes of these data before and after dam construction. Our study area covered the part of the Mekong River main channel that extends about 100 km downstream from the junction of the borders of Myanmar, Thailand, and the Lao People's Democratic Republic. We used five data validation points at 25-km intervals along this section of the river and calculated model parameters every 1 km. The years we modeled were 1990 (began dam construction) and 2006 (after dam

The 19 October 2007 removal of the 14-m-high temporary coffer dam standing in stead of Marmot Dam on the Sandy River, Oregon, triggered a rapid sequence of fluvial responses as the ~730,000 m3 of sand and gravel filling the former reservoir was suddenly exposed to an energetic river. Here we report on the rapid erosion and redeposition of this sediment in the minutes, days, and months following breaching of the coffer dam. Our analyses stem from: 1) repeat topographic surveys of the reservoir and downstream channel reach made before and after breaching and after major storm events; 2) repeat and time-lapse photography from locations around the reservoir; and 3) frequent site visits during and immediately after smaller flow events to document modest channel changes. Following mechanical notching of the earthen coffer dam at 17:00 PDT (Pacific Daylight Time), small knickpoints formed on the downstream dam face and migrated up face until they intercepted the dam crest at 17:45 PDT. This interception resulted in rapid vertical erosion of the reservoir sediment, an instantaneous peak discharge of 136 m3/s (compared to an incoming flow of 50 m3/s) as pooled reservoir water drained, and tall (e.g., 1-2 m high) knickpoints migrated upstream at rates exceeding 200 m/hr. Rapid knickpoint migration slowed 200 m upstream from the breach when the channel became superposed on a bedrock outcrop. After the river slid off the bedrock during slightly higher flow, the knickpoint declined in height and moved upstream another 300 m over the next several days at a mean rate of about 1 m/hr. Knickpoint migration over the next 1.5 km of the reservoir progressed episodically, sweeping rapidly through long (~ 400 m) pools but slowing where it intercepted bouldery riffles that had emerged. At the end of high flows in May 2008, the remnant knickpoint had migrated 2 km upstream from the former dam site, resembled a riffle crest approximately 1 m high, but remained 1.5 km downstream from the

The mortality of salmon smolts during their migration out of freshwater and into the ocean has been difficult to measure. In the Columbia River, which has an extensive network of hydroelectric dams, the decline in abundance of adult salmon returning from the ocean since the late 1970s has been ascribed in large measure to the presence of the dams, although the completion of the hydropower system occurred at the same time as large-scale shifts in ocean climate, as measured by climate indices such as the Pacific Decadal Oscillation. We measured the survival of salmon smolts during their migration to sea using elements of the large-scale acoustic telemetry system, the Pacific Ocean Shelf Tracking (POST) array. Survival measurements using acoustic tags were comparable to those obtained independently using the Passive Integrated Transponder (PIT) tag system, which is operational at Columbia and Snake Riverdams. Because the technology underlying the POST array works in both freshwater and the ocean, it is therefore possible to extend the measurement of survival to large rivers lacking dams, such as the Fraser, and to also extend the measurement of survival to the lower Columbia River and estuary, where there are no dams. Of particular note, survival during the downstream migration of at least some endangered Columbia and Snake River Chinook and steelhead stocks appears to be as high or higher than that of the same species migrating out of the Fraser River in Canada, which lacks dams. Equally surprising, smolt survival during migration through the hydrosystem, when scaled by either the time or distance migrated, is higher than in the lower Columbia River and estuary where dams are absent. Our results raise important questions regarding the factors that are preventing the recovery of salmon stocks in the Columbia and the future health of stocks in the Fraser River. PMID:18959485

The largest river-valley development to be proposed in India is that in the Narmada valley. The building of the Bargi dam, a multi-purpose irrigation and hydro-electric project, in Jabalpur, in central India, formed part of the first phase of the development of this valley (1974-1988). Many villages and several hectares of land in three districts were submerged as the waters rose behind the dam, the worst affected area being the catchment area of the primary health centre (PHC) at Narayanganj, in Mandla district. Until recently, cases of malaria were relatively rare in Narayanganj. However, an epidemic of malaria in late 1996 claimed hundreds of lives in the area and the outbreak spread, during 1997, to new villages in the region. A review of the records collected by the National Malaria Eradication Programme (NMEP) not only indicated that the slide positivity rate (SPR) for Narayanganj increased > 7.45-fold between 1979 and 1997 but also that the slide falciparum rate (SFR) increased > 32-fold over the same period. The NMEP data available for Mandla district as a whole indicated a doubling in mean SPR and SFR between 1979 and 1997. There is no evidence that a new species of vector has established since 1979. In fact, indoor-resting densities of anophelines and of the most established vector, Anopheles culicifacies, have fallen since the dam was built, but densities of another vector, An. fluviatilis, have increased. PMID:10690243

This dissertation investigates the potential impacts of canals and small dams on gravel-bed rivers and methods for documenting those impacts. First, I evaluate the potential for mapping channel depths along the McKenzie River, OR, using 10 cm resolution optical aerial imagery with a hydraulically-assisted bathymetry (HAB-2) model. Results demonstrate that channel depths can be accurately mapped in many areas, with some imagery limitations. The HAB-2 model works well in the majority of the river (R2=0.89) when comparing modeled to observed depths, but not in areas of shadow, surface turbulence, or depths >1.5 m. Next, I analyze the relative effects of a small dam and two diversion canals on sediment distribution along bars of the lower McKenzie River. The typical pattern of downstream fining is disrupted at each feature and several tributaries, particularly in the "reduced water reaches" below canal outtakes. Most modeled discharge values necessary to mobilize bar sediments fall at or below the 2-year flood return interval, with the remaining at or below the 5-year flood return interval, generally reflecting the D50 values at each bar (20-115 mm). The third analysis investigates the potential to document geomorphic impacts of small dams in Oregon at ecoregion extents using air photos and publically available data sets. This analysis highlights data disparity with respect to the collecting agency's mission and the difficulty of using remote sensing for small dams. Though the imagery was not useful in evaluating small dam impacts due to resolution and feature size, the data were useful in mapping the small dam distribution across Oregon and each ecoregion. Sixty-one percent of Oregon land is located in the catchment of at least one small dam and the greatest number of dams per area is in the Willamette Valley ecoregion. Overall, this research suggests that, while the application of these techniques must be improved, our ability to observe, study, and understand rivers

... portion of the lower Colorado River on the Arizona side between Thompson Bay and Copper Canyon. 2. Havasu..., AZ. Regulated Area The waters of the lower Colorado River encompassed by the following boundaries... Colorado River, between Davis Dam (Bullhead City, Arizona) and Headgate Dam (Parker, Arizona)....

Due to their operational flexibility, hydroelectric dams are ideal candidates to compensate for the intermittency and unpredictability of wind energy production. However, more coordinated use of wind and hydropower resources may exacerbate the impacts dams have on downstream environmental flows, that is, the timing and magnitude of water flows needed to sustain river ecosystems. In this paper, we examine the effects of increased (i.e., 5%, 15%, and 25%) wind market penetration on prices for electricity and reserves, and assess the potential for altered price dynamics to disrupt reservoir release schedules at a hydroelectric dam and cause more variable and unpredictable hourly flow patterns (measured in terms of the Richards-Baker Flashiness (RBF) index). Results show that the greatest potential for wind energy to impact downstream flows occurs at high (∼25%) wind market penetration, when the dam sells more reserves in order to exploit spikes in real-time electricity prices caused by negative wind forecast errors. Nonetheless, compared to the initial impacts of dam construction (and the dam's subsequent operation as a peaking resource under baseline conditions) the marginal effects of any increased wind market penetration on downstream flows are found to be relatively minor. PMID:25061693

deposited within the sediment wedge and within the gorge, whereas eroded sand largely passed through the gorge and was broadly dispersed farther downstream. The sequence of transporting flows affected the specific trajectory of reservoir erosion and downstream sediment transport during the 2 years following breaching. However, because the overall erosion was largely a consequence of knickpoint retreat and channel widening, which in the 2 years after removal had affected most of the reservoir reach, it is unlikely that the specific sequence of flows significantly affected the overall outcome. Because the knickpoint had largely passed through the reservoir within 2 years, and the remaining reservoir sediment is mostly isolated high above armored or bedrock banks, it is unlikely that substantial additional sediment from the reservoir site will enter the system unless very large flows occur. Continued channel evolution downstream of the dam site is probable as deposits formed in the first 2 years are episodically mobilized. Below the Sandy River gorge, detection of effects related to release of reservoir sediment is challenging, especially in areas of sand deposition, because of the high background supply of sand in the river and substantial channel dynamism.

The construction of Glen Canyon Dam, completed in 1963, resulted in substantial physical and biological changes to downstream Colorado River environments between Lake Powell and Lake Mead - an area almost entirely within Grand Canyon National Park, Ariz. In an effort to understand these changes, data have been collected to assess the condition of a number of downstream resources. In terms of measuring water quality, the collection of specific-conductance data is a cost-effective method for estimating salinity. Data-collection activities were initially undertaken by the Bureau of Reclamation's Glen Canyon Environmental Studies (1982-96); these efforts were subsequently transferred to the U.S. Geological Survey's Grand Canyon Monitoring and Research Center (1996 to the present). This report describes the specific-conductance dataset collected for the Colorado River between Glen Canyon Dam and Diamond Creek from 1988 to 2007. Data-collection and processing methods used during the study period are described, and time-series plots of the data are presented. The report also includes plots showing the relation between specific conductance and total dissolved solids. Examples of the use of specific conductance as a natural tracer of parcels of water are presented. Analysis of the data indicates that short-duration spikes and troughs in specific-conductance values lasting from hours to days are primarily the result of flooding in the Paria and Little Colorado Rivers, Colorado River tributaries below Glen Canyon Dam. Specific conductance also exhibits seasonal variations owing to changes in the position of density layers within the reservoir; these changes are driven by inflow hydrology, meteorological conditions, and background stratification. Longer term trends in Colorado River specific conductance are reflective of climatological conditions in the upper Colorado River Basin. For example, drought conditions generally result in an increase in specific conductance in Lake

Dam removal continues to garner attention as a potential river restoration tool. The increasing possibility of dam removal through the FERC relicensing process, as well as through federal and state agency actions, makes a critical examination of the ecological benefits and costs essential. This paper reviews the possible ecological impacts of dam removal using various case studies. Restoration of an unregulated flow regime has resulted in increased biotic diversity through the enhancement of preferred spawning grounds or other habitat. By returning riverine conditions and sediment transport to formerly impounded areas, riffle/pool sequences, gravel, and cobble have reappeared, along with increases in biotic diversity. Fish passage has been another benefit of dam removal. However, the disappearance of the reservoir may also affect certain publicly desirable fisheries. Short-term ecological impacts of dam removal include an increased sediment load that may cause suffocation and abrasion to various biota and habitats. However, several recorded dam removals have suggested that the increased sediment load caused by removal should be a short-term effect. Pre-removal studies for contaminated sediment may be effective at controlling toxic release problems. Although monitoring and dam removal studies are limited, a continued examination of the possible ecological impacts is important for quantifying the resistance and resilience of aquatic ecosystems. Dam removal, although controversial, is an important alternative for river restoration. PMID:11393315

This report summarizes results of the first year of a study initiated in September 1984 to evaluate the adequacy of channel modifications made in the lower Umatilla River to improve adult anadromous salmonid passage to Three Mile Dam (RKm 5.6), determine if fish passage or delay problems exist at Three Mile Dam and recommend site specific corrective measures if needed. Movements of steelhead (Salmo gairdneri) were monitored using mark and recapture and radio telemetry techniques. Thirty-four steelhead were marked with T-anchor tags and released in the lower river. Fifteen of those marked were also fitted with radio transmitters. Three radiotagged steelhead migrated through channel modifications to Three Mile Dam. Two of these fish migrated to the dam in less than 26 hours, but held just below the dam for 7 and 10 days before entering the ladders. The third steelhead delayed for 30 days and entered the west ladder within 24 hours of arrival at the dam. Two other radiotagged steelhead moved upstream through some of the channel modifications but did not migrate to the dam. Only one of 19 marked steelhead not fitted with transmitters was recovered at Three Mile Dam. 14 refs., 18 figs., 3 tabs.

The removal of Milltown Dam in 2008 from the Clark Fork River, Montana, USA, lowered base level at the dam site by 9 m and triggered erosion of nearly 600,000 metric tons of predominantly fine reservoir sediment. Bedload and bed-material sampling, repeat topographic surveys, sediment transport modeling, geochemical fingerprinting of downstream sediments, and Lidar analysis have all been applied to study the upstream and downstream effects of the dam removal. In the years since dam breaching, successive years with similar peak flows (3-year recurrence interval) were followed by a third year with below-average runoff. Nearly all of the documented reservoir erosion occurred in the first year, when sand and silt was eroded and transported downstream. In subsequent years, minimal reservoir erosion occurred, in part as a result of active management to prevent further reservoir erosion, but coarse material eroded from the reservoir has dispersed downstream. Upstream responses in this system have been strongly mediated by Superfund remediation activities in Milltown Reservoir, in which over two million metric tons of contaminated sediments have been mechanically excavated. Downstream aggradation has been limited in the main channel but was initially substantial in bars and side channels of a multi-thread reach 21 to 25 km downstream of the dam site, suggesting that channel change has been influenced far more by the antecedent depositional environment than by proximity to the source of the sediment pulse. Comparison of observed erosion with pre-removal modeling shows that reservoir erosion exceeded model predictions by two orders of magnitude in the unconfined Clark Fork arm of the reservoir. In addition, fine reservoir sediments predicted to move exclusively in suspension traveled as bedload at lower transport stages. The resulting fine sediment deposition in substrate interstices, on bars, and in side channels of the gravel- and cobble-bed Clark Fork River is the most

The Marmot dam, a medium-large sized dam on the Sandy River in Oregon, was removed in October 2007 to restore fish spawning habitat. This decommissioning project provided the opportunity to study fluvial geomorphologic changes as affected by the release of impounded sediment behind a dam. This research project examined change in grain size distribution (GSD) in Reach B in the downstream of the Sandy River, relatively close to the dam site. Data was collected in July 2008 and compared to data collected by others in July 2007, prior to the dam removal. Seven bars in this reach were facies mapped and pebble counted using the Wolman pebble counting technique. This study hypothesized that fine material had already traveled downstream without deposition whereas larger grains had yet to be transported to this reach. Therefore, Reach B should not have changed significantly since the dam removal. Data collected in 2008 suggest that the GSD of some individual bars changed though these changes are not apparent when evaluating the reach as a whole. In Reach B1, one of the three bars had noticeable changes in the size of finer grains though in contrast, the change in fraction of sand for the other two bars was more evident. In Reach B2, where four bars were studied, only one showed a noticeable change in D16. The data suggest that grain size in Reach B2 changed less than in Reach B1. Overall thus far, grain size in Reach B appears to be fairly the same, pre- and post-dam removal.

In 1906, the Bureau of Reclamation created Jackson Lake Dam on the Snake River in what later became Grand Teton National Park. The geomorphic, hydrologic and vegetation adjustments downstream of the dam have yet to be documented. After a larger reservoir was completed further downstream in 1957, the reservoir release schedule from Jackson Lake Dam was changed in a manner that lowered the magnitude and frequency of floods. The stability of the Snake River exhibited a complex response to the change in flow regime. Close to major tributaries, the Snake River increased in total sinuosity and rates of lateral channel migration. Away from the influence of tributaries, the river experienced fewer avulsions and a decrease in sinuosity. Vegetation maps were constructed from 1945 and 1989 aerial photography and field surveys. Using these data, we determined how vegetation is directly related to the number of years since each portion of the floodplain was last occupied by the channel. The vegetation has changed from a flood-pulse dominated mosaic to a more terrestrial-like pattern of succession. Changes in the Snake River and its floodplain have direct implications on bald eagle habitat, moose habitat, fish habitat, safety of rafting and canoeing, and biodiversity at the community and species levels.

In 2007, the U.S. Geological Survey, Watercourse Engineering, and the Bureau of Reclamation began a project to construct and calibrate a water quality and hydrodynamic model of the 21-mile reach of the Klamath River from Link RiverDam to Keno Dam. To provide a basis for this work, data collection and experimental work were planned for 2007 and 2008. This report documents sampling and analytical methods and presents data from the first year of work. To determine water velocities and discharge, a series of cross-sectional acoustic Doppler current profiler (ADCP) measurements were made on the mainstem and four canals on May 30 and September 19, 2007. Water quality was sampled weekly at five mainstem sites and five tributaries from early April through early November, 2007. Constituents reported here include field parameters (water temperature, pH, dissolved oxygen concentration, specific conductance); total nitrogen and phosphorus; particulate carbon and nitrogen; filtered orthophosphate, nitrite, nitrite plus nitrate, ammonia, organic carbon, iron, silica, and alkalinity; specific UV absorbance at 254 nm; phytoplankton and zooplankton enumeration and species identification; and bacterial abundance and morphological subgroups. The ADCP measurements conducted in good weather conditions in May showed that four major canals accounted for most changes in discharge along the mainstem on that day. Direction of velocity at measured locations was fairly homogeneous across the channel, while velocities were generally lowest near the bottom, and highest near surface, ranging from 0.0 to 0.8 ft/s. Measurements in September, made in windy conditions, raised questions about the effect of wind on flow. Most nutrient and carbon concentrations were lowest in spring, increased and remained elevated in summer, and decreased in fall. Dissolved nitrite plus nitrate and nitrite had a different seasonal cycle and were below detection or at low concentration in summer. Many nutrient and

Mohawk Dam, part of the Muskingum basin flood control system, was built in 1938 and is operated by the U.S. Army Corps of Engineers (Corps). Since this high-hazard dam could not survive a probable maximum flood (PMF), the Corps conducted a study to determine the least expensive means of enabling the dam to survive a PMF. Applying a previously proposed framework to select the social cost minimizing capacity of a dam, we show that Mohawk Dam had sufficient capacity that any retrofit has a social cost larger than expected benefits. Sensitivity analyses were performed adjusting the peak flow distribution, the costs of modification, and downstream flood damage, as well as the possibility of loss of life. For any reasonable value of these variables the conclusion does not change that the structure already met so high a safety goal regarding extreme floods that no retrofit is needed. Using risk-based methods to perform reservoir safety evaluations, as recommended by a National Research Council committee in 1985, is indeed feasible. Furthermore, their use provides valuable insight and guidance into the selection of strategies to enhance the safety of dams.

The Bureau of Reclamation proposes to administer the construction of fish passage and protective facilities at Three Mile Falls Diversion Dam on the Umatilla River in Oregon to increase the numbers of anadromous fish. The Bonneville Power Administration (BPA) proposes to provide funding for the project. These agencies' actions would implement section 904(d) of the Northwest Power Planning Council's Columbia River Basin Fish and Wildlife Program which addresses the provision of offsite enhancement to compensate for fish and wildlife losses caused by hydroelectric project development and operations throughout the Columbia River Basin. This Finding of No Significant Impact (FONSI) is the National Environmental Policy Act (NEPA) decision document for both agencies. The proposed action would improve both upstream and downstream passage by providing a new right bank ladder on Three Mile Falls Diversion Dam, modifying the existing left bank ladder, and installing rotary drum fish screens and related structures on the adjacent West Extension Irrigation District (WEID) Canal. Four other alternatives are considered in the environmental assessment (EA): a concrete apron plus a left bank ladder; a cap on the crest of the dam plus a left bank ladder; dam removal; and no action. 5 figs., 6 tabs.

Proposed construction of a series of locks and dams in the Red River in Louisiana will cause a permanent increase in average river stage. The potentiometric surface of the shallow alluvial aquifer and the water table in the fine-grained material confining the aquifer will be affected. The purpose of this study, using digital-modeling techniques, was to predict the average postconstruction potentiometric surface (steady state) and the water table (nonsteady state) so that potential effects of the water-level changes could be evaluated. Plans for lock and dam 4 at realined mile 154 (kilometer 250) above the mouth of the Red River call for a pool elevation of 115 feet (35 meters) and will cause an average increase in river stage ranging from 24 to 4.5 feet (7 to 1.4 meters). As a result, ground-water levels will be raised 1 foot (0.3 meter) or more between the Red River and Bayou Pierre from the dam to Coushatta , and below Campti, east of the river. The potentiometric surface may be at or near land surface in low areas between the Red River and Bayou Pierre, and above land surface locally upstream from the dam. The magnitude of ground-water-level fluctuations near the river will be reduced to less than half the present range.

Two dams on the Elwha River, Washington State, USA trapped over 20 million m3 of mud, sand, and gravel since 1927, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams, initiated in September 2011, induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the geomorphic response of a coastal delta to these increases. Detailed measurements of beach topography and nearshore bathymetry show that ~ 2.5 million m3 of sediment was deposited during the first two years of dam removal, which is ~ 100 times greater than deposition rates measured prior to dam removal. The majority of the deposit was located in the intertidal and shallow subtidal region immediately offshore of the river mouth and was composed of sand and gravel. Additional areas of deposition include a secondary sandy deposit to the east of the river mouth and a muddy deposit west of the mouth. A comparison with fluvial sediment fluxes suggests that ~ 70% of the sand and gravel and ~ 6% of the mud supplied by the river was found in the survey area (within about 2 km of the mouth). A hydrodynamic and sediment transport model, validated with in-situ measurements, shows that tidal currents interacting with the larger relict submarine delta help disperse fine sediment large distances east and west of the river mouth. The model also suggests that waves and currents erode the primary deposit located near the river mouth and transport sandy sediment eastward to form the secondary deposit. Though most of the substrate of the larger relict submarine delta was unchanged during the first two years of dam removal, portions of the seafloor close to the river mouth became finer, modifying habitats for biological communities. These results show that river restoration, like natural changes in river sediment supply, can result in rapid and substantial coastal geomorphological responses.

SummaryTiete River System in the State of Sao Paolo, Brazil is characterized by complex hydraulics and operational problems due to series of dams and point and diffuse inflows along the river. A one dimension Lagrangian river model was developed and applied to the 313 km reach of the Upper and Middle Tiete River Basin from the Penha Dam to the head water of Bara Bonita Reservoir, a stretch of river that includes six small to medium size dams (3.4-22 m high) including the Pirapora Reservoir and 26 inflows into the river (11 tributaries, 9 diffuse source areas, and discharges of 4 cities stormwater and 2 wastewater treatment plants. The conservative tracer transport and temperature model that accounts for the short and long wave radiation and heat transfers at the free surface was included and solved using the Crank-Nicholson scheme. The time variable catchment input to the model was the simulated output of the external hydrological model called Runoff Load Model which results were provided by CETESB. The numerical treatment of series of dams and spillway (that included uncontrolled overflow spillway, gate-controlled ogee spillway; and underflow gates and tunnels) and parameterisation of hydraulic jumps are described. Special attention was focused on the high spatial and temporal variation of flows in Tiete River Basin, a result of the large variation in catchment inflows and channel geometry due to dams and reservoirs along the river. Predicted and measured spatial and seasonal variation of flow and temperature profiles along the river show good agreement. The simulated travel time of conservative tracer is compared against the CETESB's 1982 and 1984 field study data in a 254 km reach of the Middle Tiete River that again shows good agreement. Being Lagrangian in construction, this new model is computationally efficient making it an ideal tool for long term simulation for water resource planning, management and operation decision making in a large and complex river

Two recent dam removals on tributaries to the Columbia River in the northwestern United States present contrasting examples of how dam removal methods, reservoir contents, and geomorphic settings influence system responses. The 2008 removal of Milltown Dam, from the Clark Fork River (CFR), Montana, and the 2011 removal of Condit Dam from the White Salmon River (WSR), Washington (Table 1), represent two of the largest dam removals to date. The Milltown Dam removal was notable because the dam stored millions of cubic meters of contaminated mine tailings, a portion of which were excavated as part of Superfund remediation but a portion of which flowed downstream after the removal. On the CFR, post-breach high flows in 2008 produced reservoir erosion and downstream deposition in bed interstices, along bars, and on the floodplain, but above-average (3-15 year recurrence interval) floods since then have remobilized this material and have, to a large extent, erased signs of downstream sedimentation. The Condit Dam removal entailed dynamiting of a 4m by 5.5m hole at the base of the dam, which produced rapid and dramatic draining of fine reservoir sediments within hours of the blast. Downstream of Condit Dam, the initial hyperconcentrated flows and sediment pulse draped the WSR with fine sediment, filled pools, and, in an unconfined reach influenced by the Columbia River's backwater, caused meters of aggradation and new bar formation. In the confined, bedrock-dominated reach downstream of the Condit site, pool-riffle structure has started to reemerge as of summer 2012 and the finest bed materials have been evacuated from the main channel, although sediment storage in pools and eddies persists. Whereas post-breach geomorphic responses on the CFR have been largely driven by hydrology, the post-breach evolution of the WSR has been predominantly influenced by antecedent geomorphic conditions (slope, confinement, and Columbia River backwater). On both the CFR and WSR, the pace of

Although sediment supply is recognized as a fundamental driver of fluvial processes, measuring how dams affect sediment regimes and incorporating such knowledge into management strategies remains challenging. To determine the influences of damming, tributary supply, and valley morphology and sediment storage on downstream sediment supply in a dryland river, the Bill Williams River (BWR) in western Arizona, we measured basin erosion rates using cosmogenic nuclide analysis of beryllium-10 (10Be) at sites upstream and downstream of a dam along the BWR, as well as from tributaries downstream of the dam. Riverbed sediment mixing calculations were used to test if the dam, which blocks sediment supply from the upper 85% of the basin's drainage area, increases the proportion of tributary sediment to residual upstream sediment in mainstem samples downstream of the dam. Erosion rates in the BWR watershed are more than twice as large in the upper catchment (136 t km-2 yr-1) than in tributaries downstream of Alamo Dam (61 t km-2 yr-1). Tributaries downstream of the dam have little influence on mainstem sediment dynamics. The effect of the dam on reducing sediment supply is limited, however, because of the presence of large alluvial valleys along the mainstem BWR downstream of the dam that store substantial sediment and mitigate supply reductions from the upper watershed. These inferences, from our 10Be derived erosion rates and mixing calculations, are consistent with field observations of downstream changes in bed material size, which suggest that sediment-deficit conditions are restricted to a 10 km reach downstream of the dam, and limited reservoir bathymetry data. Many studies have suggested that tributary sediment inputs downstream of dams play a key role in mitigating dam-induced sediment deficits, but here we show that in a dryland river with ephemeral tributaries, sediment stored in alluvial valleys can also play a key role and in some cases trumps the role of

As 10.5 million t (7.1 million m3) of sediment was released from two former reservoirs, downstream dispersion of a sediment wave caused widespread bed aggradation of ~ 1 m (greater where pools filled), changed the river from pool–riffle to braided morphology, and decreased the slope of the lowermost river. The newly deposited sediment, which was finer than most of the pre-dam-removal bed, formed new bars (largely pebble, granule, and sand material), prompting aggradational channel avulsion that increased the channel braiding index by almost 50%. As a result of mainstem bed aggradation, floodplain channels received flow and accumulated new sediment even during low to moderate flow conditions. The river system showed a two- to tenfold greater geomorphic response to dam removal (in terms of bed elevation change magnitude) than it had to a 40-year flood event four years before dam removal. Two years after dam removal began, as the river had started to incise through deposits of the initial sediment wave, ~ 1.2 million t of new sediment (~ 10% of the amount released from the two reservoirs) was stored along 18 river km of the mainstem channel and 25 km of floodplain channels. The Elwha River thus was able to transport most of the released sediment to the river mouth. The geomorphic alterations and changing bed sediment grain size along the Elwha River have important ecological implications, affecting aquatic habitat structure, benthic fauna, salmonid fish spawning and rearing potential, and riparian vegetation. The response of the river to dam removal represents a unique opportunity to observe and quantify fundamental geomorphic processes associated with a massive sediment influx, and also provides important lessons for future river-restoration endeavors.

Dam removal is important for reconnecting river habitats and restoring the free flow of water and sediment, so managing accumulated sediments is crucial in dam removal planning as the cost and potential impacts of dam removal can vary substantially depending on local conditions. A key uncertainty in dam removal is the fate of reservoir sediment stored upstream of the dam. Release of impounded sediment could raise downstream bed elevations leading to flooding, increase lateral channel mobility leading to bank erosion, and potentially bury downstream ecologically sensitive habitats if the sediment is fine. The ability to predict the sediment impacts of dam removal in highly sediment-filled systems is thus increasingly important as the number of such dam-removal cases is growing. Due to the safety concerns and the need for habitat restoration for the Formosan landlocked salmon, the Shei-Pa National Park in Taiwan removed the 15m high Chijiawan "No. 1 Check Dam" in late May 2011. During the planning process prior to removal, we conducted field surveys, numerical simulations, and flume experiments to determine sediment impacts and to suggest appropriate dam removal strategies. We collected river-bed topography and sediment bulk samples in 2010 to establish the channel geometry and grain-size distribution for modeling input. The scaled flume experiment was designed to provide insights on how and if the position of a notch location and size would affect the rate and amount of reservoir erosion under particular discharges. Observations indicated that choices of notch location can force the river to migrate differently. For long-term prediction, we used the quasi-two-dimensional numerical model NETSTARS (Network of Stream Tube model for Alluvial River Simulation) to simulate the channel responses. These simulations indicated that high suspended sediment concentrations would be the most likely major concern in the first year, while concerns for downstream sediment deposition

In 2012 and 2013, Pacific Northwest National Laboratory (PNNL) conducted a study that summarized the passage route proportions and route-specific survival rates of steelhead kelts that passed through Federal Columbia River Power System (FCRPS) dams. To accomplish this, a total of 811 steelhead kelts were tagged with Juvenile Salmon Acoustic Telemetry System (JSATS) transmitters. Acoustic receivers, both autonomous and cabled, were deployed throughout the FCRPS to monitor the downstream movements of tagged kelts. Kelts were also tagged with passive integrated transponder tags to monitor passage through juvenile bypass systems (JBS) and detect returning fish. The current study evaluated data collected in 2012 and 2013 to identify environmental, temporal, operational, individual, and behavioral variables that were related to forebay residence time, route of passage, and survival of steelhead kelts at FCRPS dams on the Snake River. Multiple approaches, including 3-D tracking, bivariate and multivariable regression modeling, and decision tree analyses were used to identify the environmental, temporal, operational, individual, and behavioral variables that had the greatest effect on forebay residence time, route of passage, and route-specific and overall dam passage survival probabilities for tagged kelts at Lower Granite (LGR), Little Goose (LGS), and Lower Monumental (LMN) dams. In general, kelt behavior and discharge appeared to work independently to affect forebay residence times. Kelt behavior, primarily approach location, migration depth, and “searching” activities in the forebay, was found to have the greatest influence on their route of passage. The condition of kelts was the single most important factor affecting their survival. The information gathered in this study may be used by dam operators and fisheries managers to identify potential management actions to improve in-river survival of kelts or collection methods for kelt reconditioning programs to aid

We assessed the effects of lowhead dams on the EPT group (ephemeropterans, plecopterans, and trichopterans) by sampling habitat and macroinvertebrates monthly from November 2000 to October 2001 at eight gravel bars centered around two lowhead dams on the Neosho River, Lyon County, Kansas. Sites included a reference and treatment site upstream and downstream from each dam. Percent EPT was greater at reference sites than upstream treatment sites, and was positively correlated with stream velocity and %gravel in the substrate, but negatively correlated with substrate compaction and %boulder in the substrate. These results are similar to those for large dams and suggest that differences in habitat around these lowhead dams are unfavorable for EPT taxa, a finding important to the conservation and restoration of biotic integrity in riverine ecosystems.

The Klamath River once supported large runs of anadromous salmonids. Water temperature associated with multiple mainstem hydropower facilities might be one of many factors responsible for depressing Klamath salmon stocks. We combined a water quantity model and a water quality model to predict how removing the series of dams below Upper Klamath Lake might affect water temperatures, and ultimately fish survival, in the spawning and rearing portions of the mainstem Klamath. We calibrated the water quantity and quality models and applied them for the hydrometeorological conditions during a 40-year postdam period. Then, we hypothetically removed the dams and their impoundments from the models and reestimated the river's water temperatures. The principal thermal effect of dam and reservoir removal would be to restore the timing (phase) of the river's seasonal thermal signature by shifting it approximately 18 days earlier in the year, resulting in river temperatures that more rapidly track ambient air temperatures. Such a shift would likely cool thermal habitat conditions for adult fall chinook (Oncorhynchus tshawytscha) during upstream migration and benefit mainstem spawning. By contrast, spring and early summer temperatures could be warmer without dams, potentially harming chinook rearing and outmigration in the mainstem. Dam removal might affect the river's thermal regime during certain conditions for over 200 km of the mainstem. PMID:15726283

Removal of two dams 32 m and 64 m high on the Elwha River, Washington, USA, provided the first opportunity to examine river response to a dam removal and controlled sediment influx on such a large scale. Although many recent river-restoration efforts have included dam removal, large dam removals have been rare enough that their physical and ecological effects remain poorly understood. New sedimentary deposits that formed during this multi-stage dam removal result from a unique, artificially created imbalance between fluvial sediment supply and transport capacity. River flows during dam removal were essentially natural and included no large floods in the first two years, while draining of the two reservoirs greatly increased the sediment supply available for fluvial transport. The resulting sedimentary deposits exhibited substantial spatial heterogeneity in thickness, stratal-formation patterns, grain size and organic content. Initial mud deposition in the first year of dam removal filled pore spaces in the pre-dam-removal cobble bed, potentially causing ecological disturbance but not aggrading the bed substantially at first. During the second winter of dam removal, thicker and in some cases coarser deposits replaced the early mud deposits. By 18 months into dam removal, channel-margin and floodplain deposits were commonly >0.5 m thick and, contrary to pre-dam-removal predictions that silt and clay would bypass the river system, included average mud content around 20%. Large wood and lenses of smaller organic particles were common in the new deposits, presumably contributing additional carbon and nutrients to the ecosystem downstream of the dam sites. Understanding initial sedimentary response to the Elwha Riverdam removals will inform subsequent analyses of longer-term sedimentary, geomorphic and ecosystem changes in this fluvial and coastal system, and will provide important lessons for other river-restoration efforts where large dam removal is planned or

Construction of large dams on the Upper-Mekong River, China, has significant social impacts on local communities. To analyze the social impacts, we identified three classes of wealth for the affected people, material, embodied, and relational, and comprehensively compared the loss and compensation in each type of wealth. Then we examined the effects on gap of wealth at household and community levels. Lastly, an insider-outsider analysis was conducted to understand the differences in the perceptions of wealth loss between local villagers and policy makers, and recommendations for more reasonable compensation policies were provided. PMID:23380304

The Swiss Rhone River was systematically embanked during the period 1864-1893. The Swiss Rhone River valley is a glacial valley filled by glaciolacustrine, fluvioglacial and fluvial sediments. Torrential tributaries contribute to a large extent to the sedimentation in the valley and have built large alluvial fans in the main valley. The period before the riverdamming corresponds to the Little Ice Age, and it is supposed that the torrential behaviour of the river and its tributaries was very active during that period. In parallel to a large hydraulic project (Third Rhone River Correction), aiming at enlarging the river for security and environmental reasons, this project aims at reconstructing the palaeogeomorphology of the river floodplain before and also during the 30-year long embankment project developed during the last decades of the 19th century. The objective is to better know the geomorphological behaviour of the river, and also to localize palaolandforms (meanders, braided patterns, sandstone dunes, wetlands, etc.), present in the floodplain in the first part of the 19th century and that have now totally disappeared. The project is carried out in close collaboration with the Cantonal Archives of Valais and with a group of historians working on the relations between the river and the communities. It should contribute to a better knowledge of the Swiss Rhone River history (Reynard et al., 2009). Both published official maps (Dufour maps, Siegfried maps) and unpublished maps and plans are systematically collected, digitized, and organised in a database managed by a Geographical Information System. Other data are collected (place names, geomorphological, hydrological and hydraulic data, information about land-use and vegetation, paintings and photographs, etc.) and localised. A high-resolution digital terrain model and areal photographs are also used and allow us to map palaeolandforms (meanders, filled oxbow lakes, former channels, etc.). In a second step

As aging dams become obsolete or economically inefficient, dam removal has become an important aspect of river restoration in recent years. While various efforts are ongoing to enhance our understanding, studies documenting the physical and ecological responses to dam removal are still lacking, particularly for removal of large dams in mountain river and following major flood, where the size of watersheds and the amount of reservoir sediment released can be much greater than for most previously studied dam removals. This presentation documents the geomorphic evolution to removal of a large dam on a coarse-grained, steep (an order of magnitude greater than on the Marmot) mountain channel in Taiwan. The Chijiawan creek is the only habitat in Taiwan of the endangered Formosan landlocked salmon. Its habitat has been cut significantly since the 1960s following construction of check dams designed to prevent reservoir sedimentation downstream. The largest and lowermost barrier on Chijiawan creek is the 15m high, "No. 1 Check Dam" built in 1971. Forty years later, the dam had backfilled with about an estimated 0.2 million m3 sediment and its toe had been scoured about 4m below its foundation, raising a significant risk of dam failure. For these reasons, the Shei-Pa National Park removed the dam in late May 2011. To monitor the channel response to dam removal, we conducted surveys of grain size distributions, cross-sectional and longitudinal profiles, analyzed the stage and turbidity records, and carried out repeat photography. Channel changes were greatest immediately following removal as a result of the high stream power, steep energy slope, and unconsolidated alluvial fill behind the dam. Headcut propagation caused immediate removal of the sand-grade sediment and progressive channel widening. One month after dam removal, a minor flood event with the estimated peak discharge of 20 m3/s excavated a big wedge of sediment from the impoundment. Two months after dam removal

Large landslides that form channel blockages have the potential to inhibit or enhance local channel incision. Inhibitive effects include mantling of the channel bed with large caliber debris at the landslide site and with alluvium accumulated upstream of the blockage site. Incision enhancement downstream of the blockage site may result from catastrophic dam breach floods, with peak discharges potentially many times greater than those of meteorologically generated floods. Here, we use a 1-D finite difference model of longitudinal profile evolution to explore the implications of such processes for long-term (106 yr) incision patterns and morphologic development. We use simple rules to represent blockage-related perturbations to the rate of "background incision," which is driven by excess shear stress or stream power. The recurrence interval of landslides and the height of blockages are loosely constrained by field data from central and eastern Oregon. Scenarios simulated include a random spatial distribution of landslides; spatial clustering of landslides; temporal clustering of landslides; and variable rates of base-level lowering combined with landsliding. Spatial clustering of landslides in the downstream reaches of the evolving profile, such as we document in parts of central and eastern Oregon, has the greatest effect on local incision rate and long- wavelength profile morphology, reducing long-term incision rates by up to 50% in the most affected reaches and creating convexities in the channel profile with amplitudes of 100s of meters. These effects are amplified when coupled with rapid base level fall. Randomly distributed landslides slightly increase the overall convexity of the channel profile and create knickpoints that persist even after complete erosion of the blockages and associated aggradational wedges. In contrast, spatial clustering of landslides in the upper reaches of the profile, temporal clustering of landsliding, and landsliding coupled with

Resource managers are increasingly being challenged by stakeholder groups to consider dam removal as a policy option and as a tool for watershed management. As more dam owners face high maintenance costs, and rivers as spawning grounds for anadromous fish become increasingly valuable, dam removal may provide the greatest net benefit to society. This article reviews the impact of Endangered Species Act listings for anadromous fish and recent shifts in the Federal Energy Regulatory Commission's hydropower benefit-costs analysis and discusses their implications for dam removal in California. We propose evaluative criteria for consideration of dam removal and apply them to two case studies: the Daguerre and Englebright Dams on the Yuba River and the Scott and Van Horne Dams on the South Eel River, California. PMID:11568839

Hydroelectric dams represent major investments and major sources of environmental and social impacts. Powerful forces surround the decision-making process on public investments in the various options for the generation and conservation of electricity. Brazil’s proposed Belo Monte Dam (formerly Kararaô) and its upstream counterpart, the Altamira Dam (better known by its former name of Babaquara) are at the center of controversies on the decision-making process for major infrastructure projects in Amazonia. The Belo Monte Dam by itself would have a small reservoir area (440 km2) and large installed capacity (11, 181.3 MW), but the Altamira/Babaquara Dam that would regulate the flow of the Xingu River (thereby increasing power generation at Belo Monte) would flood a vast area (6140 km2). The great impact of dams provides a powerful reason for Brazil to reassess its current policies that allocate large amounts of energy in the country’s national grid to subsidized aluminum smelting for export. The case of Belo Monte and the five additional dams planned upstream (including the Altamira/Babaquara Dam) indicate the need for Brazil to reform its environmental assessment and licensing system to include the impacts of multiple interdependent projects.

Hydroelectric dams represent major investments and major sources of environmental and social impacts. Powerful forces surround the decision-making process on public investments in the various options for the generation and conservation of electricity. Brazil's proposed Belo Monte Dam (formerly Kararaô) and its upstream counterpart, the Altamira Dam (better known by its former name of Babaquara) are at the center of controversies on the decision-making process for major infrastructure projects in Amazonia. The Belo Monte Dam by itself would have a small reservoir area (440 km2) and large installed capacity (11, 181.3 MW), but the Altamira/Babaquara Dam that would regulate the flow of the Xingu River (thereby increasing power generation at Belo Monte) would flood a vast area (6140 km2). The great impact of dams provides a powerful reason for Brazil to reassess its current policies that allocate large amounts of energy in the country's national grid to subsidized aluminum smelting for export. The case of Belo Monte and the five additional dams planned upstream (including the Altamira/Babaquara Dam) indicate the need for Brazil to reform its environmental assessment and licensing system to include the impacts of multiple interdependent projects. PMID:16738820

Some scholars have argued that the formation and outburst of an ancient dammed lake in the Jishi Gorge at ca. 3700 cal yr BP resulted in the destruction of Lajia, the site of a famous prehistoric disaster in the Guanting Basin, upper Yellow River valley, China. However, the cause of the dammed lake and the exact age of the dam breaching are still debated. We investigated ancient landslides and evidence for the dammed lake in the Jishi Gorge, including dating of soil from the shear zone of an ancient landslide, sediments of the ancient dammed lake, and loess above lacustrine sediments using radiocarbon and optically stimulated luminescence (OSL) dating methods. Six radiocarbon dates and two OSL dates suggested that the ancient landslides and dammed lake events in the Jishi Gorge probably occurred around 8100 cal yr BP, and the ancient dammed lake was breached between 6780 cal yr BP and 5750 cal yr BP. Hence, the outburst of the ancient dammed lake in the Jishi Gorge was unrelated to the ruin of the Lajia site, but likely resulted in flood disasters in the Guanting Basin around 6500 cal yr BP.

A gravel bar has been recognized as ecologically significant in that they provide simplified habitat with topographical, hydrological and thermo-chemical diversity, while enhancing material exchanges as interfaces laterally between aquatic and terrestrial habitats, and vertically between surface and subsurface waters. During past several decades, regulated rivers below dams have been loss of a number of the geomorphological features due to sediment starvation by upstream dams, accompanied by a subsequent degradation of their ecological functions. Despite a growing concern for gravel bar management recognizing its importance in recovering riverine ecosystem services, the ecological roles of gravel bars have not been assessed enough from the empirical perspectives of habitat diversity and organic matter interactions. In this study, we investigate the 'natural filtering effects' for reducing lentic plankton and contaminants associated with self-purification, and 'physicochemical habitat complexity' of gravel bars, focusing on reach-scaled gravel bars in rivers located in three different countries; First is the Uji River in central Japan, where there has been a loss of gravel bars in the downstream reaches since an upstream dam was constructed in 1965; second is the Tagliamento River in northeast Italy, which shows morphologically intact braided bar channels by natural flooding events and sediment supply; third is the Trinity River in the United States (located in northern California), the site of ongoing restoration efforts for creating new gravel bars through gravel augmentation and channel rehabilitation activities. We traced the downstream changes in particulate organic matter (POM) trophic sources (composed of allochthonous terrestrial inputs, autochthonous instream production and lentic plankton from dam outflows) in order to evaluate the roles of the geomorphological features in tailwater ecosystem food-resources shifting. We calculated suspended POM

Characterizing the physical and biological characteristics of the lower Elwha River, its estuary, and adjacent nearshore habitats prior to dam removal is essential to monitor changes to these areas during and following the historic dam-removal project set to begin in September 2011. Based on the size of the two hydroelectric projects and the amount of sediment that will be released, the Elwha River in Washington State will be home to the largest river restoration through dam removal attempted in the United States. Built in 1912 and 1927, respectively, the Elwha and Glines Canyon Dams have altered key physical and biological characteristics of the Elwha River. Once abundant salmon populations, consisting of all five species of Pacific salmon, are restricted to the lower 7.8 river kilometers downstream of Elwha Dam and are currently in low numbers. Dam removal will reopen access to more than 140 km of mainstem, flood plain, and tributary habitat, most of which is protected within Olympic National Park. The high capture rate of river-borne sediments by the two reservoirs has changed the geomorphology of the riverbed downstream of the dams. Mobilization and downstream transport of these accumulated reservoir sediments during and following dam removal will significantly change downstream river reaches, the estuary complex, and the nearshore environment. To introduce the more detailed studies that follow in this report, we summarize many of the key aspects of the Elwha River ecosystem including a regional and historical context for this unprecedented project.

Proposed construction of a series of locks and dams in the Red River in Louisiana will cause a permanent increase in average river stage. The potentiometric surface of the shallow alluvial aquifer and the water table in the fine-grained material confining the aquifer will be affected. The purpose of this study, using digital-modeling techniques, was to predict the average postconstruction potentiometric surface (steady state) and the water table (nonsteady state) so that potential effects of the water-level changes could be evaluated. Plans for lock and dam 3 at realined mile 111 (kilometer 179) above the mouth of the Red River call for a pool elevation of 87 feet (27 meters) and will cause an average increase in river stage ranging from 21 to 3.5 feet (l.4 to 1.1 meters). As a result, ground-water levels will be raised to near land surface in low areas east of the river from the damsite to Aloha and in a 0.5-mile (0.8-kilometer) strip along the west side extending 9 miles (14 kilometers) above the dam. The potentiometric surface may be above land surface locally near the dam. The magnitude of ground-water-level fluctuations near the river will be reduced to less than half the preconstruction range.

Due to their nutrient recycling function and their importance in food-webs, macroinvertebrates are essential for the functioning of aquatic ecosystems. These organisms also constitute an important component of biodiversity. Sediment evaluation and monitoring is an essential aspect of ecosystem monitoring since sediments represent an important component of aquatic habitats and are also a potential source of contamination. In this study, we focused on macroinvertebrate communities within run-of-riverdams, that are prime areas for sediment and pollutant accumulation. Little is known about littoral macroinvertebrate communities within run-of-riverdam or their response to sediment levels and pollution. We therefore aimed to evaluate the following aspects: the functional and structural composition of macroinvertebrate communities in run-of-riverdams; the impact of pollutant accumulation on such communities, and the most efficient scales and tools needed for the biomonitoring of contaminated sediments in such environments. Two run-of-riverdams located in the French alpine area were selected and three spatial scales were examined: transversal (banks and channel), transversal x longitudinal (banks/channel x tail/middle/dam) and patch scale (erosion, sedimentation and vegetation habitats). At the patch scale, we noted that the heterogeneity of littoral habitats provided many available niches that allow for the development of diversified macroinvertebrate communities. This implies highly variable responses to contamination. Once combined on a global 'banks' spatial scale, littoral habitats can highlight the effects of toxic disturbances. PMID:21272919

Glen Canyon Dam has caused a fundamental change in the distribution of fine sediment storage in the 99-km reach of the Colorado River in Marble Canyon, Grand Canyon National Park, Arizona. The two major storage sites for fine sediment (i.e., sand and finer material) in this canyon river are lateral recirculation eddies and the main-channel bed. We use a combination of methods, including direct measurement of sediment storage change, measurements of sediment flux, and comparison of the grain size of sediment found in different storage sites relative to the supply and that in transport, in order to evaluate the change in both the volume and location of sediment storage. The analysis shows that the bed of the main channel was an important storage environment for fine sediment in the predam era. In years of large seasonal accumulation, approximately 50% of the fine sediment supplied to the reach from upstream sources was stored on the main-channel bed. In contrast, sediment budgets constructed for two short-duration, high experimental releases from Glen Canyon Dam indicate that approximately 90% of the sediment discharge from the reach during each release was derived from eddy storage, rather than from sandy deposits on the main-channel bed. These results indicate that the majority of the fine sediment in Marble Canyon is now stored in eddies, even though they occupy a small percentage (???17%) of the total river area. Because of a 95% reduction in the supply of fine sediment to Marble Canyon, future high releases without significant input of tributary sediment will potentially erode sediment from long-term eddy storage, resulting in continued degradation in Marble Canyon. Copyright 2006 by the American Geophysical Union.

Dam removal has been increasingly proposed as a river restoration technique. In 2011, two large hydroelectric dams will be removed from Washington State’s Elwha River. Ten anadromous fish populations are expected to recolonise historical habitats after dam removal. A key to understanding watershed recolonisation is the collection of spatially continuous information on fish and aquatic habitats. A riverscape approach with an emphasis on biological data has rarely been applied in mid-sized, wilderness rivers, particularly in consecutive years prior to dam removal. Concurrent snorkel and habitat surveys were conducted from the headwaters to the mouth (rkm 65–0) of the Elwha River in 2007 and 2008. This riverscape approach characterised the spatial extent, assemblage structure and patterns of relative density of Pacific salmonids. The presence of dams influenced the longitudinal patterns of fish assemblages, and species richness was the highest downstream of the dams, where anadromous salmonids still have access. The percent composition of salmonids was similar in both years for rainbow trout, Oncorhynchus mykiss (Walbaum), coastal cutthroat trout, Oncorhynchus clarkii clarkii (Richardson) (89%; 88%), Chinook salmon, Oncorhynchus tshawytscha (Walbaum) (8%; 9%), and bull trout, Salvelinus confluentus (Suckley) (3% in both years). Spatial patterns of abundance for rainbow and cutthroat trout (r = 0.76) and bull trout (r = 0.70) were also consistent between years. Multivariate and univariate methods detected differences in habitat structure along the river profile caused by natural and anthropogenic factors. The riverscape view highlighted species-specific biological hotspots and revealed that 60–69% of federally threatened bull trout occurred near or below the dams. Spatially continuous surveys will be vital in evaluating the effectiveness of upcoming dam removal projects at restoring anadromous salmonids.

Dam construction is one of the main factors resulting in riverine sediment changes, which in turn cause river degradation or aggradation downstream. The main objective of this work is to examine the sediment budget affected by a sequence of dams constructed upstream in the lower reach of the Red River. The study is based on the longer-term annual data (1960-2010) with a complementary daily water and sediment data set (2008-2010). The results showed that the stretch of the river changed from sediment surplus (suggesting possible deposition processes) into sediment deficit (possible erosion processes) after the first dam (Thac Ba Dam) was constructed in 1972 and changed back to deposition after the second dam (Hoa Binh Dam) was constructed in 1985. The annual sediment deposition varied between 1.9 Mt/y and 46.7 Mt/y with an annual mean value of 22.9 Mt/y (1985-2010). The sediment deposition at the lower reach of the Red River would accelerate river aggradation which would change river channel capacity in the downstream of the Red River. The depositional processes could be sustained or changed back to erosional processes after more dams (the amount of sediment deposit was much less after the latest two dams Tuyen Quang Dam in 2009 and Sonla Dam in 2010) are constructed, depending on the water and sediment dynamics. This study revealed that the erosional and depositional processes could be shifted for the same stretch of river as affected by a sequence of dams and provides useful insights in river management in order to reduce flood frequency along the lower reach of the Red River.

Two adaptive management programs, the Glen Canyon Dam Adaptive Management Program (GCDAMP) and the Trinity River Restoration Program (TRRP) are examined. In both cases, the focus is on managing the aquatic and riparian systems downstream of a large dam and water supply project. The status of the two programs, lessons learned by the program managers and the Adaptive Environmental Assessment and Management (AEAM) evolution of the TRRP are discussed. The Trinity River illustrates some of the scientific uncertainities that a program faces and the ways the program evolves from concept through implementation.

We report on our progress from April 2002 through March 2003 on determining the effects of mitigative measures on productivity of white sturgeon populations in the Columbia River downstream from McNary Dam, and on determining the status and habitat requirements of white sturgeon populations in the Columbia and Snake rivers upstream from McNary Dam.

We report on our progress from April 2001 through March 2002 on determining the effects of mitigative measures on productivity of white sturgeon populations in the Columbia River downstream from McNary Dam, and on determining the status and habitat requirements of white sturgeon populations in the Columbia and Snake rivers upstream from McNary Dam.

This report documents development of computational fluid dynamics (CFD) models that were applied to The Dalles spillway for the US Army Corps of Engineers, Portland District. The models have been successfully validated against physical models and prototype data, and are suitable to support biological research and operations management. The CFD models have been proven to provide reliable information in the turbulent high-velocity flow field downstream of the spillway face that is typically difficult to monitor in the prototype. In addition, CFD data provides hydraulic information throughout the solution domain that can be easily extracted from archived simulations for later use if necessary. This project is part of an ongoing program at the Portland District to improve spillway survival conditions for juvenile salmon at The Dalles. Biological data collected at The Dalles spillway have shown that for the original spillway configuration juvenile salmon passage survival is lower than desired. Therefore, the Portland District is seeking to identify operational and/or structural changes that might be implemented to improve fish passage survival. Pacific Northwest National Laboratory (PNNL) went through a sequence of steps to develop a CFD model of The Dalles spillway and tailrace. The first step was to identify a preferred CFD modeling package. In the case of The Dalles spillway, Flow-3D was as selected because of its ability to simulate the turbulent free-surface flows that occur downstream of each spilling bay. The second step in development of The Dalles CFD model was to assemble bathymetric datasets and structural drawings sufficient to describe the dam (powerhouse, non-overflow dam, spillway, fish ladder entrances, etc.) and tailrace. These datasets are documented in this report as are various 3-D graphical representations of The Dalles spillway and tailrace. The performance of the CFD model was then validated for several cases as the third step. The validated model

In this study, methods and approaches were developed and tested to assess changes in contaminant fluxes resulting from dam removal in a riverine system. Sediment traps and passive samplers were deployed to measure particulate and dissolved polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in the water column prior to and following removal of a small, low-head dam in the Pawtuxet River, an urbanized river located in Cranston, RI, USA. During the study, concentrations of particulate and dissolved PAHs ranged from 21.5 to 103 μg/g and from 68 to 164 ng/L, respectively. Overall, temporal trends of PAHs showed no increases in either dissolved or particulate phases following removal of the dam. Dissolved concentrations of PCBs were very low, remaining below 1.72 ng/L at all sites. Particulate PCB concentrations across sites and time showed slightly greater variability, ranging from 80 to 469 ng/g, but with no indication that dam removal influenced any increases. Particulate PAHs and PCBs were sampled continuously at the site located below the dam and did not show sustained increases in concentration resulting from dam removal. The employment of passive sampling technology and sediment traps was highly effective in monitoring the concentrations and flux of contaminants moving through the river system. Variations in river flow had no effect on the concentration of contaminants in the dissolved or particulate phases, but did influence the flux rate of contaminants exiting the river. Overall, dam removal did not cause measurable sediment disturbance or increase the concentration or fluxes of dissolved or particulate PAHs and PCBs. This is due in large part to low volumes of impounded sediment residing above the dam and highly armored sediments in the river channel, which limited erosion. Results from this study will be used to improve methods and approaches that assess the short- and long-term impacts ecological restoration activities such as

The highest rates of change in the areal extents of channel and riparian features were observed during the pre‑2001 period, which was longer and relatively wetter than the post-2001 period. A series of tributary floods in 1997, 1998, and 2006 increased channel complexity and floodplain connectivity. During the post-2006 period, managed-flow releases, in the absence of tributary flooding, combined with gravel augmentation and mechanical restoration, caused localized increases in sediment supply and transport capacity that led to smaller, but measurable, increases in channel complexity and floodplain connectivity in the upper river near Lewiston Dam. Extensive pre-2001 channel widening and the muted geomorphic response of channel rehabilitation sites to post-2001 managed flows highlight the need for continued monitoring and assessment of the magnitude, duration, and timing of prescriptive flows and associated geomorphic responses.

The Usoi dam was created in the winter of 1911 after an enormous seismogenic rock slide completely blocked the valley of the Bartang River in the Pamir Mountains of southeastern Tajikistan. At present the dam impounds 17 million cubic meters of water in Lake Sarez. Flood volume and discharge estimates were made for several landslide generated floods that could overtop the dam. For landslide volumes of 200, 500, and 1,000 million cubic meters, estimated overtopping flood volumes were 2, 22, and 87 million cubic meters of water, respectively. Estimated peak discharge at the dam for these three flood scenarios were 57,000, 490,000, and 1,580,000 m3/s, based on triangular hydrographs of 70-, 90-, and 110-s durations, respectively. Flood-routing simulations were made for the three landslide-induced overtopping floods over a 530-km reach of the Bartang and Panj Rivers below the Usoi dam. A one-dimensional flow model using a Riemann numerical solution technique was selected for the analysis. For the 87 million cubic meter volume overtopping flood scenario, the peak flows were approximately 1, 100, 800, and 550 m3/s at locations 50, 100, and 150 km downstream of the dam respectively. ?? Springer 2006.

We examined the effects of the Mogi-Guaçu riverdamming (São Paulo State, Brazil) on the Chironomidae fauna. Pre, during, and post-filling sampling was carried out in the main channel and margins of one site in the upper zone of the reservoir, using a modified Petersen grab (325 cm2). We evaluated the total, subfamily, and tribe densities and also their relative abundance. Analysis of genera included densities, relative abundance, richness, and dominance. The Rosso's ecological value index (EVI) determined the ecological importance of each genus. There was a tendency of decrease of the total Chironomidae density, increase in the percentage of Chironomini, and decrease in densities and percentages of Orthocladiinae and Tanytarsini. These changes in percentage were respectively related to Polypedilum, Lopescladius, and Rheotanytarsus, the genera with the highest EVI values. After-filling richness was lower in the margins and dominance of genera did not change significantly. Chironomidae in the margins was more sensitive to damming than in the main channel. This difference in sensibility sustains the use of Chironomidae as bioindicators. Damming impact was indicated by the reduction of both genera richness in the margins and relative abundance of groups typical of faster waters. The results have highlighted the need for multi-habitat analysis combined with a before-after sampling approach in the environmental impact studies concerning the damming impact on the benthic fauna. PMID:26934147

/ Rivers transport sediment from eroding uplands to depositional areas near sea level. If the continuity of sediment transport is interrupted by dams or removal of sediment from the channel by gravel mining, the flow may become sediment-starved (hungry water) and prone to erode the channel bed and banks, producing channel incision (downcutting), coarsening of bed material, and loss of spawning gravels for salmon and trout (as smaller gravels are transported without replacement from upstream). Gravel is artificially added to the River Rhine to prevent further incision and to many other rivers in attempts to restore spawning habitat. It is possible to pass incoming sediment through some small reservoirs, thereby maintaining the continuity of sediment transport through the system. Damming and mining have reduced sediment delivery from rivers to many coastal areas, leading to accelerated beach erosion. Sand and gravel are mined for construction aggregate from river channel and floodplains. In-channel mining commonly causes incision, which may propagate up- and downstream of the mine, undermining bridges, inducing channel instability, and lowering alluvial water tables. Floodplain gravel pits have the potential to become wildlife habitat upon reclamation, but may be captured by the active channel and thereby become instream pits. Management of sand and gravel in rivers must be done on a regional basis, restoring the continuity of sediment transport where possible and encouraging alternatives to river-derived aggregate sources.KEY WORDS: Dams; Aquatic habitat; Sediment transport; Erosion; Sedimentation; Gravel mining PMID:9175542

The Tennessee Valley Authority (TVA) has routinely monitored dissolved oxygen (DO) and temperature from the tailwater releases of its dams since the 1950s. The original objective of this monitoring was to collect baseline information to support reaeration research and determine the relative impact of impoundments on the assimilative capacity of the river system. This monitoring has continued even though the original objective was satisfied. New purposes for this monitoring data have arisen in support of several programs, without new consideration of the monitoring strategy and sampling design. The primary purpose of this report is to compare the historical release data for 30 dams in the Tennessee Valley based on four different objectives: (1) comparison of seasonal patterns, (2) comparison of baseline conditions using descriptive statistics, (3) evaluation of monotonic trends, and (4) discussion of monitoring strategies that might be required to determine compliance with existing and proposed criteria. A secondary purpose of the report is to compile the existing database into tables and figures that would be useful for other investigators. 51 refs., 210 figs., 1 tab.

The Elwha River restoration project, in Washington State, includes the largest dam-removal project in United States history to date. Starting September 2011, two nearly century-old dams that collectively contained 21 ± 3 million m3 of sediment were removed over the course of three years with a top-down deconstruction strategy designed to meter the release of a portion of the dam-trapped sediment. Gauging with sediment-surrogate technologies during the first two years downstream from the project measured 8,200,000 ± 3,400,000 tonnes of transported sediment, with 1,100,000 and 7,100,000 t moving in years 1 and 2, respectively, representing 3 and 20 times the Elwha River annual sediment load of 340,000 ± 80,000 t/y. During the study period, the discharge in the Elwha River was greater than normal (107% in year 1 and 108% in year 2); however, the magnitudes of the peak-flow events during the study period were relatively benign with the largest discharge of 292 m3/s (73% of the 2-year annual peak-flow event) early in the project when both extant reservoirs still retained sediment. Despite the muted peak flows, sediment transport was large, with measured suspended-sediment concentrations during the study period ranging from 44 to 16,300 mg/L and gauged bedload transport as large as 24,700 t/d. Five distinct sediment-release periods were identified when sediment loads were notably increased (when lateral erosion in the former reservoirs was active) or reduced (when reservoir retention or seasonal low flows and cessation of lateral erosion reduced sediment transport). Total suspended-sediment load was 930,000 t in year 1 and 5,400,000 t in year 2. Of the total 6,300,000 ± 3,200,000 t of suspended-sediment load, 3,400,000 t consisted of silt and clay and 2,900,000 t was sand. Gauged bedload on the lower Elwha River in year 2 of the project was 450,000 ± 360,000 t. Bedload was not quantified in year 1, but qualitative observations using bedload

We evaluated Renibaeterium salmoninarum infection in smolts of hatchery and wild spring-summer Chinook salmon Oncorhynchus tshawytscha sampled during most of the outmigration at Little Goose (1988) and Lower Granite dams (1988–1991) on the Snake River and at Priest Rapids and McNary dams on the Columbia River (1988–1990). We sampled 860–2,178 fish per dam each year. Homogenates of kidney–spleen tissue from all fish were tested for the presence of R. salmoninarum antigens by the enzyme-linked immunosorbent assay (ELISA), and homogenates from 10% of the fish were examined by the fluorescent antibody technique (FAT). Although only 1–11% of fish sampled at a given dam during any l year exhibited lesions characteristic of bacterial kidney disease, 86–100% of the fish tested positive for R. salmoninarum antigen by ELISA, whereas 4–17% of the fish tested positive by the FAT. During most years, a majority (68–87%) of fish testing positive by the ELISA had low R. salmoninarum antigen levels, but in 1989, 53% of positive fish from Lower Granite Dam and 52% from McNary Dam showed medium-to-high antigen levels. For most years, the highest mean antigen levels were measured in fish sampled after 75% of the total out-migrants had passed a given dam. When the largest numbers of fish were being collected for bypass or downriver transportation, mean antigen levels were relatively low.

Sedgeunkedunk Stream, a third-order tributary to the Penobscot River, Maine, historically supported several anadromous fishes, including the Atlantic Salmon Salmo salar, AlewifeAlosa pseudoharengus, and Sea Lamprey Petromyzon marinus. However, two small dams constructed in the 1800s reduced or eliminated spawning runs entirely. In 2009, efforts to restore marine–freshwater connectivity in the system culminated with removal of the lowermost dam, thus providing access to an additional 4.6 km of lotic habitat. Because Sea Lampreys utilized accessible habitat prior to dam removal, they were chosen as a focal species with which to quantify recolonization. During spawning runs of 2008–2011 (before and after dam removal), individuals were marked with PIT tags and their activity was tracked with daily recapture surveys. Open-population mark–recapture models indicated a fourfold increase in the annual abundance of spawning-phase Sea Lampreys, with estimates rising from 59±4 () before dam removal (2008) to 223±18 and 242±16 after dam removal (2010 and 2011, respectively). Accompanying the marked increase in annual abundance was a greater than fourfold increase in nesting sites: the number of nests increased from 31 in 2008 to 128 and 131 in 2010 and 2011, respectively. During the initial recolonization event (i.e., in 2010), Sea Lampreys took 6 d to move past the former dam site and 9 d to expand into the furthest upstream reaches. Conversely, during the 2011 spawning run, Sea Lampreys took only 3 d to penetrate into the upstream reaches, thus suggesting a potential positive feedback in which larval recruitment into the system may have attracted adult spawners via conspecific pheromone cues. Although more research is needed to verify the migratory pheromone hypothesis, our study clearly demonstrates that small-stream dam removal in coastal river systems has the potential to enhance recovery of declining anadromous fish populations.

The Usoi dam was created in the winter of 1911 after an enormous seismogenic rock slide completely blocked the valley of the Bartang River in the Pamir Mountains of southeastern Tajikistan. At present the dam impounds 17 million cubic meters of water in Lake Sarez. Flood volume and discharge estimates were made for several landslide generated floods that could overtop the dam. For landslide volumes of 200, 500, and 1,000 million cubic meters, estimated overtopping flood volumes were 2, 22, and 87 million cubic meters of water, respectively. Estimated peak discharge at the dam for these three flood scenarios were 57,000, 490,000, and 1,580,000 cubic meters per second, based on triangular hydrographs of 70-, 90-, and 110-second durations, respectively. Flood-routing simulations were made for the three landslide-induced overtopping floods over a 530-kilometer reach of the Bartang and Panj Rivers below the Usoi dam. A one-dimensional flow model using a Riemann numerical solution technique was selected for the study. A constant 50-meter wide rectangular channel, which represented the mean channel width, was used for the entire reach. A roughness coefficient of 0.038, appropriate for steep mountainous streams, also was used for the entire reach. For the 87 million cubic meter volume overtopping flood scenario, the peak flows were approximately 1,100, 800, and 550 cubic meters per second at locations 50, 100, and 150 kilometers downstream of the dam, respectively. The model was also used to simulate the less likely scenario of an instantaneous dam breach and draining of the total volume of the lake. Simulated peak flows were approximately 64,000, 52,000, 40,000, and 20,000 cubic meters per second at locations 50, 100, 150, and 530 kilometers downstream of the Usoi dam.

Global biodiversity in river and riparian ecosystems is generated and maintained by geographic variation in stream processes and fluvial disturbance regimes, which largely reflect regional differences in climate and geology. Extensive construction of dams by humans has greatly dampened the seasonal and interannual streamflow variability of rivers, thereby altering natural dynamics in ecologically important flows on continental to global scales. The cumulative effects of modification to regional-scale environmental templates caused by dams is largely unexplored but of critical conservation importance. Here, we use 186 long-term streamflow records on intermediate-sized rivers across the continental United States to show that dams have homogenized the flow regimes on third- through seventh-order rivers in 16 historically distinctive hydrologic regions over the course of the 20th century. This regional homogenization occurs chiefly through modification of the magnitude and timing of ecologically critical high and low flows. For 317 undammed reference rivers, no evidence for homogenization was found, despite documented changes in regional precipitation over this period. With an estimated average density of one dam every 48 km of third- through seventh-order river channel in the United States, dams arguably have a continental scale effect of homogenizing regionally distinct environmental templates, thereby creating conditions that favor the spread of cosmopolitan, nonindigenous species at the expense of locally adapted native biota. Quantitative analyses such as ours provide the basis for conservation and management actions aimed at restoring and maintaining native biodiversity and ecosystem function and resilience for regionally distinct ecosystems at continental to global scales. PMID:17360379

Dam-influenced floodplain morphology has not been studied extensively in post-glacial rivers with high densities of colonial-era milldams. Fluvial restoration in the eastern U.S. often focuses on understanding the natural, or pre-Colonial, floodplain processes. Recent work by Walter and Merritts (2008) in the piedmont of the U.S. Mid-Atlantic region suggests milldams significantly impact sedimentation by creating surfaces composed of post-dam legacy sediment that are often abandoned by the river and function as fill terraces. This work has not yet been tested in a post-glacial environment. I analyze channel morphology and sedimentation patterns upstream of two breached dams on the Sheepscot River in Mid-Coastal Maine using lidar digital elevation models, historical aerial photographs, radiocarbon dating, and hydraulic modeling. In the past several decades, observable channel morphologic changes occurred at the two study sites: Maxcy’s Mills dam (built in 1809, it was 4-m high and breached in the late 1950s), and at Head Tide dam (built in the 1760s, it is 6-m high and was partially breached in 1952). The Sheepscot River is one of Maine’s eight rivers with native anadromous Atlantic salmon populations. Because Atlantic salmon are a federally listed endangered species, understanding the existence and transport of legacy sediment has become an important component of habitat restoration efforts in the region. The goal of this investigation is to determine the extent of legacy sediment in order to better understand how historical dam sites affect morphology and sediment transport in a post-glacial, low-gradient river system. Field and remote sensing analyses indicate that surfaces (up to 2-m high) composed of mud and sand function as floodplains 1.5-2.5 km upstream of both former dam sites. Preliminary analysis of seven radiocarbon dates from pieces of tree bark sampled from the stratigraphy (58-187 cm below the surface) of the two study sites suggest at least 1.8 m

Four dams on the Kalamazoo River between the cities of Plainwell and Allegan, Mich., are in varying states of disrepair. The Michigan Department of Environmental Quality (MDEQ) and U.S. Environmental Protection Agency (USEPA) are considering removing these dams to restore the river channels to pre-dam conditions. This study was initiated to identify sediment characteristics, monitor sediment transport, and predict sediment resuspension and deposition under varying hydraulic conditions. The mathematical model SEDMOD was used to simulate streamflow and sediment transport using three modeling scenarios: (1) sediment transport simulations for 730 days (Jan. 2001 to Dec. 2002), with existing dam structures, (2) sediment transport simulations based on flows from the 1947 flood at the Kalamazoo River with existing dam structures, and (3) sediment transport simulations based on flows from the 1947 flood at the Kalamazoo River with dams removed. Sediment transport simulations based on the 1947 flood hydrograph provide an estimate of sediment transport rates under maximum flow conditions. These scenarios can be used as an assessment of the sediment load that may erode from the study reach at this flow magnitude during a dam failure. The model was calibrated using suspended sediment as a calibration parameter and root mean squared error (RMSE) as an objective function. Analyses of the calibrated model show a slight bias in the model results at flows higher than 75 m3/s; this means that the model-simulated suspended-sediment transport rates are higher than the observed rates; however, the overall calibrated model results show close agreement between simulated and measured values of suspended sediment. Simulation results show that the Kalamazoo River sediment transport mechanism is in a dynamic equilibrium state. Model results during the 730-day simulations indicate significant sediment erosion from the study reach at flow rates higher than 55 m3/s. Similarly, significant

... accordance with 33 CFR 165.7(a) and in a manner that provides as much notice to the public as possible. The... and Dam to Lake Michigan including Des Plaines River, Chicago Sanitary and Ship Canal, Chicago River... River, Chicago Sanitary and Ship Canal, Chicago River, and Calumet-Saganashkee Channel, Chicago, IL....

In 2012 and 2013, Pacific Northwest National Laboratory conducted a study that summarized the passage proportions and route-specific survival rates of steelhead kelts that passed through Federal Columbia River Power System (FCRPS) dams. To accomplish this, a total of 811 steelhead kelts were tagged with Juvenile Salmon Acoustic Telemetry System (JSATS) transmitters. Acoustic receivers, both autonomous and cabled, were deployed throughout the FCRPS to monitor the downstream movements of tagged-kelts. Kelts were also tagged with Passive Integrated Transponder tags to monitor passage through juvenile bypass systems and detect returning fish. The current study evaluated data collected in 2012 and 2013 to identify individual, behavioral, environmental and dam operation variables that were related to passage and survival of steelhead kelts that passed through FCRPS dams. Bayesian model averaging of multivariable logistic regression models was used to identify the environmental, temporal, operational, individual, and behavioral variables that had the highest probability of influencing the route of passage and the route-specific survival probabilities for kelts that passed Lower Granite (LGR), Little Goose (LGS), and Lower Monumental (LMN) dams in 2012 and 2013. The posterior probabilities of the best models for predicting route of passage ranged from 0.106 for traditional spill at LMN to 0.720 for turbine passage at LGS. Generally, the behavior (depth and near-dam searching activity) of kelts in the forebay appeared to have the greatest influence on their route of passage. Shallower-migrating kelts had a higher probability of passing via the weir and deeper-migrating kelts had a higher probability of passing via the JBS and turbines than other routes. Kelts that displayed a higher level of near-dam searching activity had a higher probability of passing via the spillway weir and those that did less near-dam searching had a higher probability of passing via the JBS and

Vegetation changes in the canyon of the Colorado River between Glen Canyon Dam and Lake Mead were studied by comparing photographs taken prior to completion of Glen Canyon Dam in 1963 with photographs taken afterwards at the same sites. In general, the older pictures show an absence of riparian plants along the banks of the river. The newer photographs of each pair were taken in 1972 through 1976 and reveal an increased density of many plant species. Exotic species, such as saltcedar and camel-thorn, and native riparian plants such as sandbar willow, arrowweed, desert broom and cattail, now form a new riparian community along much of the channel of the Colorado River between Glen Canyon Dam and Lake Mead. The matched photographs also reveal that changes have occurred in the amount of sand and silt deposited along the banks. Detailed maps are presented showing distribution of 25 plant species along the reach of the Colorado River studied. Data showing changes in the hydrologic regime since completion of Glen Canyon Dam are presented. (Kosco-USGS)

Restoration of rivers and their associated ecosystems is a growing priority for government agencies (e.g., NOAA, USDA), as well as conservation organizations. Dam removal is a major component of many restoration projects credited with reintroducing fish species, improving water ...

Restoration of rivers and their associated ecosystems is a growing priority for government agencies (e.g., NOAA, USEPA), as well as conservation organizations. Dam removal is a major component of many restoration projects credited with reintroducing fish species, improving water...

Restoration of rivers and their associated ecosystems is a growing priority for government agencies (e.g., NOAA, USEPA), as well as conservation organizations. Dam removal is a major component of many restoration projects credited with reintroducing fish species, improving water...

Many studies have assessed the effects of large dams on fishes and macroinvertebrates, but few have examined the effects of lowhead dams. We sampled fishes, macroinvertebrates, habitat, and physicochemistry monthly from November 2000 to October 2001 at eight gravel bar sites centered around two lowhead dams on the Neosho River, Kansas. Sites included a reference site and a treatment site both upstream and downstream from each dam. Multivariate analysis of variance indicated that habitat, but not physicochemistry, varied immediately upstream and down-stream from the dams, with resultant effects on macroinvertebrate and fish assemblages. Compared with reference sites, upstream treatment sites were deeper and had lower velocities and downstream treatment sites were shallower and had higher velocities; both upstream and downstream treatment sites had greater substrate compaction than reference sites. Macroinvertebrate richness did not differ among site types, but abundance was lowest at downstream treatment sites and evenness was lowest at upstream treatment sites. Fish species richness did not differ among site types, but abundance was highest at downstream reference sites and evenness was highest at upstream sites. The abundance of some benthic fishes was influenced by the dams, including that of the Neosho madtom Noturus placidus, which was lowest immediately upstream and downstream from dams, and those of the suckermouth minnow Phenacobius mirabilis, orangethroat darter Etheostoma spectabile, and slenderhead darter Percina phoxocephala, which were highest in downstream treatment sites. Although limited to one system during a 1-year period, this study suggests that the effects of lowhead dams on fishes, macroinvertebrates, and habitat are similar to those reported for larger dams, providing important considerations for riverine ecosystem conservation efforts.

The purpose of our study was to determine the interaction between in-stream large wood (LW), bank erosion, and sports fisheries in the 210 river kilometer (km) Coastal Plain segment of the dam-regulated Roanoke River, North Carolina. Methods included collecting background geomorphic data including a 200 km channel geometry survey and measurements from 701 bank erosion pins at 36 cross-sections over 132 km. LW concentrations were evaluated over a 177 km reach using georeferenced aerial video taken during regulated low flow (56 m3/s). LW transport was measured using 290 radio tagged LW pieces (mean diameter = 35.0 cm, length = 9.3 m) installed between 2008 and 2010. Largemouth bass (Micropterus salmoides) were surveyed in 2010 at 29 sites using a boat mounted electroshock unit. The abundance of LW in logjams was 59 pieces/km and these were concentrated (21.5 logjams/km) in an actively eroding reach with relatively high sinuosity, high local LW production rates, and narrow channel widths. Most jams (70%) are available nearly year round as aquatic habitat, positioned either on the lower bank or submerged at low-water flows. The actively eroding reach is adjusting to upstream dam regulation by channel widening. The channel upstream of this reach has widened and stabilized while the channel downstream of the eroding reach is still relatively narrow but with lower bank erosion rates. Repeat surveys of radio tagged LW determined that transport was common throughout the study area despite dam regulation and a low channel gradient (0.0016). The mean distance travelled by a radio tagged piece of LW was 11.9 km with a maximum of 101 km (84 tags moved, 96 stationary, 110 not found). Radio tagged LW that moved during the study was found at low flow either in logjams (44%), as individual LW (43%), or submerged mid-channel (14%). Largemouth bass biomass density (g/hr effort) was highest in the actively eroding reach where logjams were most common. Our results support the

Proposed construction of a series of locks and dams in the Red River in Louisiana will cause a permanent increase in average river stage. The potentiometric surface of the shallow alluvial aquifer and the water table in the fine-grained material confining the aquifer will be affected. The purpose of this study, using digital-modeling techniques, was to predict the average postconstruction potentiometric surface (steady state) and the water table (nonsteady state) so that potential effects of the water-level changes could be evaluated. Plans for lock and dam 1 at mile 44 (kilometer 71) above the mouth of the Red River call for a pool elevation of 40 feet (12.2 meters) and will cause an average increase in river stage of 9 feet (2.7 meters). As a result, ground-water levels will be raised 1 foot (0.3 meter) or more within 4 miles (6.4 kilometers) of the river. The potentiometric surface may be near land surface in low-lying areas, and above land surface along the course of drainage features near the dam. The magnitude of ground-water-level fluctuations near the river will be reduced. (Woodard-USGS)

The Mekong River basin in Southeast Asia is undergoing intensive and pervasive hydropower development to satisfy demand for increased energy and income to support its growing population of 60 million people. Just 20 years ago this river flowed freely. Today some 30 large dams exist in the basin, and over 100 more are being planned for construction. These dams will alter the river's natural water, sediment and nutrient flows, thereby impacting river morphology and ecosystems, and will fragment fish migration pathways. In doing so, they will degrade one of the world's most valuable and productive freshwater fish habitats. For those dams that have not yet been constructed, there still exist opportunities to modify their siting, design and operation (SDO) to potentially achieve a more balanced set of tradeoffs among hydropower production, sediment/nutrient passage and fish passage. We introduce examples of such alternative SDO opportunities for Sambor Dam in Cambodia, planned to be constructed on the main stem of the Mekong River. To evaluate the performance of such alternatives, we developed a Python-based simulation tool called PySedSim. PySedSim is a daily time step mass balance model that identifies the relative tradeoffs among hydropower production, and flow and sediment regime alteration, associated with reservoir sediment management techniques such as flushing, sluicing, bypassing, density current venting and dredging. To date, there has been a very limited acknowledgement or evaluation of the significant uncertainties that impact the evaluation of SDO alternatives. This research is formalizing a model diagnostic assessment of the key assumptions and parametric uncertainties that strongly influence PySedSim SDO evaluations. Using stochastic hydrology and sediment load data, our diagnostic assessment evaluates and compares several Sambor Dam alternatives using several performance measures related to energy production, sediment trapping and regime alteration, and

Together, these different scientific perspectives form a basis for understanding the Elwha River ecosystem, an environment that has and will undergo substantial change. A century of change began with the start of dam construction in 1910; additional major change will result from dam removal scheduled to begin in September 2011. This report provides a scientific snapshot of the lower Elwha River, its estuary, and adjacent nearshore ecosystems prior to dam removal that can be used to evaluate the responses and dynamics of various system components following dam removal.

Two dams on the Elwha River, Washington State, USA trapped over 20 million m3 of mud, sand, and gravel since 1927, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams, initiated in September 2011, induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the geomorphic response of a coastal delta to these increases. Detailed measurements of beach topography and nearshore bathymetry show that ~ 2.5 million m3 of sediment was deposited during the first two years of dam removal, which is ~ 100 times greater than deposition rates measured prior to dam removal. The majority of the deposit was located in the intertidal and shallow subtidal region immediately offshore of the river mouth and was composed of sand and gravel. Additional areas of deposition include a secondary sandy deposit to the east of the river mouth and a muddy deposit west of the mouth. A comparison with fluvial sediment fluxes suggests that ~ 70% of the sand and gravel and ~ 6% of the mud supplied by the river was found in the survey area (within about 2 km of the mouth). A hydrodynamic and sediment transport model, validated with in-situ measurements, shows that tidal currents interacting with the larger relict submarine delta help disperse fine sediment large distances east and west of the river mouth. The model also suggests that waves and currents erode the primary deposit located near the river mouth and transport sandy sediment eastward to form the secondary deposit. Though most of the substrate of the larger relict submarine delta was unchanged during the first two years of dam removal, portions of the seafloor close to the river mouth became finer, modifying habitats for biological communities. These results show that river restoration, like natural changes in river sediment supply, can result in rapid and substantial coastal geomorphological

The Chiloquin Dam was located at river kilometer (rkm) 1.3 on the Sprague River near the town of Chiloquin, Oregon. The dam was identified as a barrier that potentially inhibited or prevented the upstream spawning migrations and other movements of endangered Lost River suckers (Deltistes luxatus), shortnose suckers (Chasmistes brevirostris), and other fish in the Sprague River. Our research objectives in 2009 were to evaluate adult catostomid spawning migration patterns using radio telemetry to identify and describe shifts in spawning area distribution and migration behavior following the removal of Chiloquin Dam in 2008. We attached external radio transmitters to 58 Lost River suckers and 59 shortnose suckers captured at the Williamson River fish weir. A total of 17 radio-tagged Lost River suckers and one radio-tagged shortnose sucker were detected approaching the site of the former Chiloquin Dam but only two radio-tagged fish (one male Lost River sucker and one female Lost River sucker) were detected crossing upstream of the dam site. A lower proportion of radio-tagged shortnose suckers were detected migrating into the Sprague River when compared with previous years. Detections on remote passive integrated transponder (PIT) tag arrays located in the Sprague River show that although the proportion of fish coming into the Sprague River is small when compared to the number of fish crossing the Williamson River fish weir, the number of fish migrating upstream of the Chiloquin Dam site increased exponentially in the first year since its removal. These data will be used in conjunction with larval production and adult spawning distribution data to evaluate the effectiveness of dam removal in order to provide increased access to underutilized spawning habitat located further upstream in the Sprague River and to reduce the crowding of spawning fish below the dam site.

Until today, scientists have mainly studied morphological processes, channel adjustment and river restoration plans on large rivers or mountain streams. These orientations answered society's needs, especially about risk management such as bank erosion or river floods. Since the European Water Framework Directive (2001) and the obligation to reach the good ecological status for freshwater systems, the operations of river restoration refocus social demand on smaller and lower gradient streams. To reach this "good ecological status", managers of French rivers increase actions to restore ecological and sediment continuity by removing dams and weirs. In most cases these operations are not subjected to morphological monitoring because they not consist in "emblematic" removals. In this context, we observe a lack of knowledge about the functioning of low order streams and their response to such operations. The objective of this presentation is to illustrate questions arising from these operations in order to initiate a global discussion of the relevance of current practices. Thus, three different issues will be discussed. Firstly, we will suggest an interrogation about the geomorphologic specificities of the low order streams and the accuracy of current knowledge to forecast their adjustments after dam or weir removals: what are the main morphological drivers in a context of low streampower ? How long does the morphological adjustment take? If these removals do not concern large structures, what could be expected about cumulative effects of small weir removal? Secondly, we will study the contribution of the long term historical approach of the morphological structure of such systems, especially to establish their resiliency and the range of channel adjustment we can expect after historic dam removal. Finally, these previous points will lead us to discuss more widely the relevance of dam removal intervention for the development of river restoration strategies. Our

The Souhegan River is a tributary of the Merrimack River that drains a 568 km2 watershed in southern New Hampshire. The lowermost barrier on the Souhegan River was the ~4-m high Merrimack Village Dam (MVD, ~500 m upstream of the confluence with the Merrimack River), demolished and removed starting on August 6, 2008. The MVD was built in 1906 at a location where various dams have existed since the 18th century. Based on a pre-removal sediment-thickness survey, the MVD impounded at least 62,000 m3 of sediment, mostly sand. Analyses of topography, historical maps, and photographs suggest that approximately twice the area of the modern impoundment has been affected by over 200 years of damming at the site. We use monumented cross sections, longitudinal profiles, repeat photography, and sediment samples to document the response of the Souhegan River to the removal of the MVD. A base level drop of 3.9 m caused immediate incision of the sand-sized sediment, followed by channel widening. The former impoundment later segmented into a non-alluvial, bedrock and boulder controlled reach, and a quasi-alluvial sand and gravel reach with erosion and deposition modulated by vegetation on the channel banks. One year after the removal, the Souhegan River had excavated 40,300 m3 (65%) of sediment from the modern impoundment. Two years after the removal, two high-magnitude floods excavated another 10,600 m3 for a total of 50,900 m3 (82%) of sediment from the modern impoundment. The response of the Souhegan River was rapid and the channel and floodplain continue to evolve toward a quasi-equilibrium configuration. Continued response will be substantially influenced by the establishment of bank vegetation within the former impoundment and the magnitude and frequency of high discharge events. We explore implications of our findings in this sand-filled impoundment for future dam removals.

The October 2007 removal of the Marmot Dam, from the Sandy River, OR, provides an opportunity to assess the impact of increased sediment flux on a river channel. The Sandy River drains the west flank of Mt Hood and typically carries a large load of sand and gravel. The 14-meter-tall dam impounded over 750,000 m3 of sediment, only a small amount of which was removed during the decommissioning. Using a one- dimensional modeling approach, it was assessed that the river could transport the accumulated sediment without large adverse impacts downstream of the dam (Cui et al, 2008 - abstract submitted). In order to observe the actual changes to the river due to the dam removal and to test the modeled predictions, a significant monitoring effort has be in place on the Sandy River including bedload and suspended load measurements, discharge measurements, high-fidelity topographic surveys, repeat photography, multiple airborne LIDAR flights, long profile surveys, as well as mapping and characterizing the grain sizes throughout several reaches downstream of the dam. A key step in the quest to describe and predict the spatial distribution of the sediment throughout the downstream reach is to first account for all the sediment (both stored in the reservoir and supplied from upstream). Here, we examine the transport and deposition downstream of the dam through a 2-fraction sediment budget approach using the former dam as the upstream limit of the reach and choosing a the mouth of a bedrock gorge 7 km below the dam site as the downstream limit. Suspended sediment and bedload measurements taken by the USGS just below the dam site (Major et al, 2008 - abstract submitted) are combined with suspended sediment and bedload measurements collected just below the mouth of the gorge and the annual hydrograph to define the sediment fluxes into and out of the reach. Repeat surveys in the reach below the dam (Wallick et al, 2008 - abstract submitted) provide the measure of change in storage

dams. Therefore, this study gives essential information about the dam safety and related analysis. Monitoring of dams is crucial since deformation might have occurred as a result of erosion, water load, hydraulic gradients, and water saturation. The case study is the deformation measurements of Ataturk Dam. This dam was constructed on Firat River and it has importance for providing drinking water, hydroelectric power and especially irrigation. In addition, brief information is given about this dam and the methods of geodetic and non-geodetic monitoring measurements applied by various disciplines. Geodetic monitoring methods are emphasized in this study. Some results have been obtained from this method for nearly seven years are presented in this work. In addition, some deformation predictions have been made especially for the cross sections where the maximum deformations took place.

Dam construction and its impact on downstream fluvial processes may substantially alter ambient bank stability, floodplain inundation patterns, and channel morphology. Most of the world's largest rivers have been dammed, which has prompted management efforts to mitigate dam effects. Three high dams (completed between 1953 and 1963) occur along the Piedmont portion of the Roanoke River, North Carolina; just downstream, the lower part of the river flows across largely unconsolidated Coastal Plain deposits. To document bank erosion rates along the lower Roanoke River, more than 700 bank erosion pins were installed along 124 bank transects. Additionally, discrete measurements of channel bathymetry, water clarity, and presence or absence of mass wasting were documented along the entire 153-kilometer-long study reach. Amounts of bank erosion in combination with prior estimates of floodplain deposition were used to develop a bank erosion and floodplain deposition sediment budget for the lower river. Present bank erosion rates are relatively high [mean 42 milimeters per year (mm/yr)] and are greatest along the middle reaches (mean 60 mm/yr) and on lower parts of the bank on all reaches. Erosion rates were likely higher along upstream reaches than present erosion rates such that erosion rate maxima have migrated downstream. Mass wasting and water clarity also peak along the middle reaches.

Rivers transport sediment from eroding uplands to depositional areas near sea level. If the continuity of sediment transport is interrupted by dams or removal of sediment from the channel by gravel mining, the flow may become sediment-starved (hungry water) and prone to erode the channel bed and banks, producing channel incision (downcutting), coarsening of bed material, and loss of spawning gravels for salmon and trout (as smaller gravels are transported without replacement from upstream), Gravel is artificially added to the River Rhine to prevent further incision and to many other rivers in attempts to restore spawning habitat. It is possible to pass incoming sediment through some small reservoirs, thereby maintaining the continuity of sediment transport through the system. Damming and mining have reduced sediment delivery from rivers to many coastal areas, leading to accelerated beach erosion. Sand and gravel are mined for construction aggregate from river channel and floodplains. In-channel mining commonly causes incision, which may propagate up- and downstream of the mine, undermining bridges, inducing channel instability, and lowering alluvial water tables. Floodplain gravel pits have the potential to become wildlife habitat upon reclamation, but may be captured by the active channel and thereby become instream pits. Management of sand and gravel in rivers must be done on a regional basis, restoring the continuity of sediment transport where possible and encouraging alternatives to river-derived aggregate sources. 80 refs., 17 figs.

Geochemical and geomorphic data from dune fields in southwestern Nebraska provide new evidence that the Nebraska Sand Hills once migrated across the North and South Platte rivers and dammed the largest tributary system to the Missouri River. The Lincoln County and Imperial dune fields, which lie downwind of the South Platte River, have compositions intermediate between the Nebraska Sand Hills (quartz-rich) and northeastern Colorado dunes (K-feldspar-rich). The most likely explanation for the intermediate composition is that the Lincoln County and Imperial dunes are derived in part from the Nebraska Sand Hills and in part from the South Platte River. The only mechanism by which the Nebraska Sand Hills could have migrated this far south is by complete infilling of what were probably perennially dry North Platte and South Platte river valleys. Such a series of events would have required an extended drought, both for activation of eolian sand and decreased discharges in the Platte River system. A nearby major tributary of the North Platte River is postulated to have been blocked by eolian sand about 12,000 14C yr B.P. We propose that an eolian sand dam across the Plattes was constructed at about this same time.

The streamflow regimen of the Neosho River downstream from John Redmond Dam in southeastern Kansas has changed significantly since the dam's completion in 1964. The controlled releases from the dam have decreased the magnitudes of peak discharges and increased the magnitudes of low discharges. The trends in river stage for selected discharges also have changed at two of the streamflow-gaging stations--those closest to the dam. There is a significant downward trend in the stages associated with the median annual peak discharges, but no significant trend in the stages associated with the annual mean discharges, which indicates that the river channel is increasing in width but not depth or that the hflow velocity has increased at the streamflow-gaging stations. Because there were not significant trends present in precipitation, mean annual discharge, or annual peak discharge, the changes are attributed to John Redmond Dam.

During and after the planned incremental removal of two large, century-old concrete dams between 2011 and 2014, the sediment-transport regime in the lower Elwha River of western Washington will initially spike above background levels and then return to pre-dam conditions some years after complete dam removal. Measurements indicate the upper reaches of the steep-gradient Elwha River, draining the northeast section of the Olympic Mountains, carries between an estimated 120,000 and 290,000 cubic meters of sediment annually. This large load has deposited an estimated 19 million cubic meters of sediment within the two reservoirs formed by the Elwha and Glines Canyon Dams. It is anticipated that from 7 to 8 million cubic meters of this trapped sediment will mobilize and transport downstream during and after dam decommissioning, restoring the downstream sections of the sediment-starved river and nearshore marine environments. Downstream transport of sediment from the dam sites will have significant effects on channel morphology, water quality, and aquatic habitat during and after dam removal. Sediment concentrations are expected to be between 200 and 1,000 milligrams per liter during and just after dam removal and could rise to as much as 50,000 milligrams per liter during high flows. Downstream sedimentation in the river channel and flood plain will be potentially large, particularly in the lower Elwha River, an alluvial reach with a wide flood plain. Overall aggradation could be as much as one to several meters. Not all reservoir sediment, however, will be released to the river. Some material will remain on hill slopes and flood plains within the drained reservoirs in quantities that will depend on the hydrology, precipitation, and mechanics of the incising channel. Eventually, vegetation will stabilize this remaining reservoir sediment, and the overall sediment load in the restored river will return to pre-dam levels.

A travel cost demand model that uses intended trips if dams are removed and the river restored is presented as a tool for evaluating the potential recreation benefits in this counterfactual but increasingly policy relevant analysis of dam removal. The model is applied to the Lower Snake River in Washington using data from mail surveys of households in the Pacific Northwest region. Five years after dam removal, about 1.5 million visitor days are estimated, with this number growing to 2.5 million annually during years 20-100. Using the travel cost method model estimate of the value of river recreation, if the four dams are removed and the 225 km river is restored, the annualized benefits at a 6.875% discount rate would be $310 million. This gain in river recreation exceeds the loss of reservoir recreation but is about $60 million less than the total costs of the dam removal alternative. The analysis suggests this extension of the standard travel cost method may be suitable for evaluating the gain in river recreation associated with restoration of river systems from dam removal or associated with dam relicensing conditions.

Dams on the Elwha River of the Olympic Peninsula have reduced sediment transport in the river for almost a century. Following dam removal, which is slated to begin in 2008, over 14 million cubic meters of mixed grain-size sediments will be exposed in the former reservoirs, much of which will erode and transport to the Strait of Juan de Fuca. Increased supply of sediment to the strait, may end, or perhaps reverse, the current trend of erosion along the river delta and adjacent shoreline. Here we describe the history of shoreline evolution along the Elwha River delta and detail monitoring plans to track nearshore changes following dam removal. Historic data document a general trend of erosion along the delta resulting in a net loss of approx. 65,000 sq. meters of land between 1926 and 1995, although variability in erosion rates is observed over both space and time. Continued monitoring of the shoreface is planned by both U.S. Geological Survey (USGS) and Lower Elwha Klallam Tribe (LEKT) scientists. USGS scientists have also implemented a research program that includes beach and nearshore mapping, process (wave and current) monitoring, and numerical modeling of sediment dispersal. Here we will present preliminary results of this work including high-resolution seabed maps of bathymetry and sediment type and changes in the nearshore bathymetry and beach topography from semi-annual mapping using RTK GPS technologies.

Beaver have expanded in their native habitats throughout the northern hemisphere in recent decades following reductions in trapping and reintroduction efforts. Beaver have the potential to strongly influence salmon populations in the side channels of large alluvial rivers by building dams that create pond complexes. Pond habitat may improve salmon productivity or the presence of dams may reduce productivity if dams limit habitat connectivity and inhibit fish passage. Our intent in this paper is to contrast the habitat use and production of juvenile salmon on expansive floodplains of two geomorphically similar salmon rivers: the Kol River in Kamchatka, Russia (no beavers) and the Kwethluk River in Alaska (abundant beavers), and thereby provide a case study on how beavers may influence salmonids in large floodplain rivers. We examined important rearing habitats in each floodplain, including springbrooks, beaver ponds, beaver-influenced springbrooks, and shallow shorelines of the river channel. Juvenile coho salmon dominated fish assemblages in all habitats in both rivers but other species were present. Salmon density was similar in all habitat types in the Kol, but in the Kwethluk coho and Chinook densities were 3–12× lower in mid- and late-successional beaver ponds than in springbrook and main channel habitats. In the Kol, coho condition (length: weight ratios) was similar among habitats, but Chinook condition was highest in orthofluvial springbrooks. In the Kwethluk, Chinook condition was similar among habitats, but coho condition was lowest in main channel versus other habitats (0.89 vs. 0.99–1.10). Densities of juvenile salmon were extremely low in beaver ponds located behind numerous dams in the orthofluvial zone of the Kwethluk River floodplain, whereas juvenile salmon were abundant in habitats throughout the entire floodplain in the Kol River. If beavers were not present on the Kwethluk, floodplain habitats would be fully interconnected and theoretically

... regulations made effective January 1, 1928, by the Secretary of War: (a) The pool above the dam shall not be... eliminate wasting of water during an increase in river flow. (b) Whenever, due to high flows, the pool above... loss of a pool below the Twin City Dam, etc., the licensee shall temporarily discharge water at...

... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF HOMELAND SECURITY Coast Guard 33 CFR Part 100 Special Local Regulation; Annual Marine Events on the Colorado River Between Davis Dam (Bullhead City, AZ) and Headgate Dam (Parker, AZ) Within the San Diego Captain of...

Seasonal thermal variability of the Colorado River in Grand Canyon was severely decreased by closure of Glen Canyon Dam and filling of Lake Powell reservoir that was achieved in 1980. From 1973 to 2002, downstream summer river temperatures at Lees Ferry were about 18°C below pre-dam conditions, and limited juvenile native fish growth and survival. A large-scale flow experiment to improve the river's thermal regime for spawning and rearing habitat of endangered native humpback chub and other native fish in eastern Grand Canyon was conducted in Water Year 2000. Monitoring revealed warming, but well below the 16-18°C optimum for chub 124 km below the dam near the Little Colorado River confluence, and no measurable chub population increase in Grand Canyon. Fall-timed stable flow experiments to improve shoreline chub nursery habitat (2008-12) were also inconclusive relative to juvenile chub growth and recruitment. Field studies also showed that daytime warming of shoreline habitats used by fish under steady flows is limited by high daily exchange rates with main channel water. Monthly averaged and higher resolution temperature models have also been developed and used to support more recent experimental management planning. Temperature simulations have been useful for screening dam release scenarios under varied reservoir storage conditions with and without use of previously proposed but never constructed multilevel intake structures on the dam's hydroelectric units. Most importantly, modeling revealed the geophysical limits on downstream warming under existing water management and dam operating policies. Hourly unsteady flow simulations in 2006 predicted equivalent levels of average downstream river warming under either fluctuating or steady flows for a given monthly release volume. River warming observed since 2002, has resulted from reduced Lake Powell storage resulting from drier upper basin hydrology. In support of new environmental compliance on dam operations

The Mekong River and its tributaries comprise one of the most productive fish habitats in the world today. The economic value of the Mekong fishery in Lao PDR, Cambodia and Vietnam is among the highest in the world, providing income and food security to tens of millions of people. However, the construction of multiple dams in the basin will reduce sediment discharge, which will adversely impact nutrient transport and habitat quality and availability, and disrupt fish migration routes. Thus, of considerable interest is the identification of alternatives to the location, design and operation of planned hydropower dams that could improve sediment passage, enable migratory fish passage, and sustain fish production for local use. This paper describes the results of simulation studies designed to identify and evaluate such alternatives, as well as their potential impact on hydropower production. Dam sites in Cambodia and Lao PDR on tributaries and on the mainstream Mekong River will be discussed. Evaluations of sediment management techniques such as flushing, sluicing and bypassing will be discussed. This study is intended to inform decision makers in Cambodia, Lao PDR and Vietnam about potential alternatives to current plans as they prepare decisions regarding the development of over 100 hydropower dams throughout the basin.

Proposed construction of a series of locks and dams in the Red River in Louisiana will cause a permanent increase in average river stage. The potentiometric surface of the shallow alluvial aquifer and the water table in the fine-grained material confining the aquifer will be affected. The purpose of this study using digital-modeling techniques, was to predict the average postconstruction potentiometric surface (steady state) and the water table (nonsteady state) so that potential effects of the water-level changes could be evaluated. Plans for lock and dam 2 at mile 87 (kilometer 140) above the mouth of the Red River call for a pool elevation of 58 feet (17.7 meters) and will cause an average increase in river stage of 12.5 feet (3.8 meters). As a result, ground-water levels will be raised 1 foot (0.3 meter) or more within 4 miles (6.4 kilometers) of the river and will be near land surface in low areas. The potentiometric surface may be as much as 1 to 2 feet (0.3 to 0.6 meter) above land surface south of Latanier along Chatlin Lake Canal and south of the Annandale area of Alexandria. The magnitude of ground-water-level fluctuations near the river will be reduced.

This report relates quality of fish habitat to flow conditions (discharge) in the Cumberland River below Wolf Creek Dam, Kentucky. Fish species' life stages targeted for investigation included juvenile brown trout, adult brown trout, adult rainbow trout, and adult brook trout. The Physical Habitat Simulation Systems (PHABSIM) was used to evaluate effects of flow variations on fish habitat, to allow evaluation of fishery effects of various design and operational alternatives, and to provide information to assist in the overall management of this natural resource for power generation and fishery benefits.

By agreement between PacifiCorp and the Federal Energy Regulatory Commission, Condit Dam on the White Salmon River in Washington State is slated to be removed in 2011, to restore anadromous salmon habitat. Our study predicts changes in hydraulics and sedimentation from dam removal on the White Salmon River in order to assess the significance of such changes to ecosystem services provided by the river. We analyzed river users’ focus-group surveys to identify relationships between physical features of the river and ecosystem services valued by users of the White Salmon River. We used HEC-RAS and numeric solutions of sediment transport morphodynamics to predict changes to water velocity, criticality of flow, water surface width, water depth, and sediment balance at various points along the river for current conditions and for after the dam has been removed and river dynamics have stabilized. Our results indicate that several identified services are likely to be affected by hydraulic changes or sedimentation after dam removal. In general, our models suggest that the river will have more whitewater, the greater part of re-exposed river channel will be bedrock, water surface width will narrow in high demand recreation areas, and sediment is likely to accumulate significantly at the river mouth. Our analysis of use by members of the focus group suggests that the experience of whitewater boaters (kayakers in particular) is likely to be enhanced, but that general leisure and fishing uses may be impaired due to decreased accessibility.

Studies of reservoir sedimentation are vital to understanding scientific and management issues related to watershed sediment budgets, depositional processes, reservoir operations, and dam decommissioning. Here we quantify the mass, organic content, and grain-size distribution of a reservoir deposit in northern California by two methods of extrapolating measurements of sediment physical properties from cores to the entire volume of impounded material. Englebright Dam, completed in 1940, is located on the Yuba River in the Sierra Nevada foothills. A research program is underway to assess the feasibility of introducing wild anadromous fish species to the river upstream of the dam. Possible management scenarios include removing or lowering the dam, which could cause downstream transport of stored sediment. In 2001 the volume of sediments deposited behind Englebright Dam occupied 25.5% of the original reservoir capacity. The physical properties of this deposit were calculated using data from a coring campaign that sampled the entire reservoir sediment thickness (6–32 m) at six locations in the downstream ∼3/4 of the reservoir. As a result, the sediment in the downstream part of the reservoir is well characterized, but in the coarse, upstream part of the reservoir, only surficial sediments were sampled, so calculations there are more uncertain. Extrapolation from one-dimensional vertical sections of sediment sampled in cores to entire three-dimensional volumes of the reservoir deposit is accomplished via two methods, using assumptions of variable and constant layer thickness. Overall, the two extrapolation methods yield nearly identical estimates of the mass of the reservoir deposit of ∼26 × 106 metric tons (t) of material, of which 64.7–68.5% is sand and gravel. Over the 61 year reservoir history this corresponds to a maximum basin-wide sediment yield of ∼340 t/km2/yr, assuming no contribution from upstream parts of the watershed impounded by other dams. The

The Yangtze River (Changjiang) is one of the most important rivers in the world. With population increase and economic growth, the stream temperature regime of the Yangtze River has been altered to some extent by human activities, including runoff impoundment (dam construction). To assess dam-induced alterations in the temperature regime of the Yangtze River quantitatively, this paper selected two key hydrological stations (i.e. Yichang and Cuntan stations) below and above the Three Gorges dam respectively as case study sites. Cuntan station is at the upper limit of Three Gorges reservoir controlling water and sediment discharge to the reservoir from the upper Yangtze River. Yichang station is the control point of the upper Yangtze River basin and located at the starting point of the middle reach of the Yangtze River, 44 km below the Three Gorges Dam and 6 km below the Gezhouba Dam. The Gezhouba reservoir, with a capacity of 1.58 × 109m3, is a run-of-river reservoir and located on the main stem of the Yangtze River, 38 km below the Three Gorges reservoir. The Three Gorges reservoir with a capacity of 3.93 × 1010 m3 spans the Yangtze River. On the consideration that the Gezhouba Reservoir and the Three Gorges Reservoir may impose impacts on the downstream temperature regime of Gezouba and Three Gorges dams to different extents respectively, the whole study periods were divided into 3 subperiods by the years when these two reservoirs started to store water respectively. On the basis of 50-year long time series of daily or ten-day stream temperature from two stations, their annual, seasonal, monthly and daily stream temperature, the correlation of the 10-day stream temperature values between Cuntan and Yichang, and the correlation of the 10-day stream temperature changing rates between Cuntan and Yichang in different subperiods were analyzed and compared. The stream temperature rising and falling characteristics and daily stream temperature distribution during the

Populations of mink (Mustela vison) have declined in many areas of the world. Such declines have been linked to exposures to synthetic, halogenated hydrocarbons. In the Great Lakes region, mink are fewer in areas along the shore of the Great Lakes and their tributaries where mink have access to fish from the Great Lakes. Recently, there has been discussion of the relative merits of passage of fishes around hydroelectric dams on rivers in Michigan. A hazard assessment was conducted to determine the potential for adverse effects on mink, which could consume such fishes from above or below dams on the rivers. Concentrations of organochlorine insecticides, polychlorinated biphenyls (PCBs), 2,3,7,8-tetrachlordibenzo-p-dioxin equivalents (TCDD-EQ), and total mercury were measured in composite samples of fishes from above or below hydroelectric dams on the Manistee and Muskegon Rivers, which flow into Lake Michigan, and the Au Sable River, which flows into Lake Huron. Concentrations of organochlorine insecticides, PCBs, and TCDD-EQ were all greater in fishes from below the dams than those from above. Concentrations of neither organochlorine insecticides nor mercury in fishes are currently a risk to mink above or below the dams. All of the species of fishes collected from downstream of the dams contained concentrations of PCBs and TCDD-EQ, which represent a hazard to mink. The hazard index for PCBs was less than one for the average of all species from the upstream reaches of the Manistee and Au Sable Rivers, but not the Muskegon. The hazard index (concentration in fish/NOAEC) was greater than 1 for all of the species collected from below the dams, in all three rivers. The greatest hazard index was observed for carp (Cyprinus carpio) downstream on the Muskegon River. Because the concentrations of PCBs used in the hazard assessment were corrected for relative toxic potencies, the hazard ratios based on PCBs should be similar to those based on TCDD-EQ. This was found to be

Four hydropower operational scenarios at Flaming Gorge Dam were evaluated to determine their potential effects on riparian vegetation along the Green River in Utah and Colorado. Data collected in June 1992 indicated that elevation above the river had the largest influence on plant distribution. A lower riparian zone occupied the area between the approximate elevations of 800 and 4,200-cfs flows--the area within the range of hydropower operational releases. The lower zone was dominated by wetland plants such as cattail, common spikerush, coyote willow, juncus, and carex. An upper riparian zone was above the elevation of historical maximum power plant releases from the dam (4,200 cfs), and it generally supported plants adapted to mesic, nonwetland conditions. Common species in the upper zone included box elder, rabbitbrush, grasses, golden aster, and scouring rush. Multispectral aerial videography of the Green River was collected in May and June 1992 to determine the relationship between flow and the areas of water and the riparian zone. From these relationships, it was estimated that the upper zone would decrease in extent by about 5% with year-round high fluctuation, seasonally adjusted high fluctuation, and seasonally adjusted moderate fluctuation, but it would increase by about 8% under seasonally adjusted steady flow. The lower zone would increase by about 13% for both year-round and seasonally adjusted high fluctuation scenarios but would decrease by about 40% and 74% for seasonally adjusted moderate fluctuation and steady flows, respectively. These changes are considered to be relatively minor and would leave pre-dam riparian vegetation unaffected. Occasional high releases above power plant capacity would be needed for long-term maintenance of this relict vegetation.

The National Center for Earth Surface Dynamics (NCED) is an NSF funded Science and Technology Center devoted to developing a quantitative, predictive science of the ecological and physical processes that define and shape rivers and river networks. The Science Museum of Minnesota's (SMM) Earthscapes River Restoration classes provide k-12 students, teachers, and the public opportunities to explore NCED concepts and, like NCED scientists, move from a qualitative to a quantitative-based understanding of river systems. During a series of classes, students work with an experimental model of the Elwha River in Washington State to gain an understanding of the processes that define and shape river systems. Currently, two large dams on the Elwha are scheduled for removal to restore salmon habitat. Students design different dam removal scenarios to test and make qualitative observations describing and comparing how the modeled system evolves over time. In a following session, after discussing the ambiguity of the previous session's qualitative data, student research teams conduct a quantitative experiment to collect detailed measurements of the system. Finally, students interpret, critique, and compare the data the groups collected and ultimately develop and advocate a recommendation for the "ideal" dam removal scenario. SMM is currently conducting a formative evaluation of River Restoration classes to improve their educational effectiveness and guide development of an educator's manual. As of August 2006, pre- and post-surveys have been administered to 167 students to gauge student learning and engagement. The surveys have found the program successful in teaching students why scientists use river models and what processes and phenomena are at work in river systems. Most notable is the increase in student awareness of sediment in river systems. A post-visit survey was also administered to 20 teachers who used the models in their classrooms. This survey provided feedback about

The removal of two dams on the Elwha River, Washington, is the largest dam-removal project in history. Our research documents the sediment deposition, erosion, and channel changes between the dams following the initial sediment release from the removal of the upstream Glines Canyon Dam. Within the first year following the dam removal, the pulse of coarse sediment and large woody debris propagated downstream well over 6 km below the dam. The sediment deposition and altered channel hydraulics caused lateral channel migration where anabranching channels merge around new mid-channel bars and at large bends in the river channel. Documenting the river channel response to this exceptional sediment pulse could improve models of the impacts of future dam removals on similar gravel-bed rivers. We quantified the sediment flux and channel changes at four field sites 2-6 km downstream of Glines Canyon Dam. Topographic changes were surveyed with a terrestrial laser scanner (TLS) on an annual basis from August 2012 - August 2014 and the surface sediment distribution was quantified with bimonthly sediment counts. Differencing the annual TLS data yielded an overall increase in sediment throughout the study reach, with a minimum of 20,000 m3 of deposition on bars and banks exposed above the water surface in each 700-m-long TLS survey reach. The surface sediment distribution decreased from ~18 cm to < 1 mm. Large woody debris transported downstream from the former reservoir contributed to the formation of new sand and gravel bars along the channel margin at two sites as well as the longitudinal growth of several bars throughout the study area. The new bar formations have continued to propagate downstream as new sediment and woody debris have been added and remobilized, increasing the complexity of the river channel. By spring 2013, channel features that were present before the dam removal began to re-emerge due to the remobilizing of sediment through the system.

Since the closure of Glen Canyon Dam and the beginning of flow regulation of the Colorado River in Grand Canyon in 1963, considerable efforts have been directed toward understanding the aquatic ecology of this altered ecosystem. Understanding what controls resource availability has been a central focus of these efforts because the Colorado River supports populations of sport fish and endangered humpback chub, both of which appear to be strongly resource limited. There is evidence that dam discharge regime and canyon orientation influence algal standing crop due to their effects on water velocity (scour) and solar insolation, respectively. We explored whether these physical factors influenced rates of primary production and ecosystem respiration, two different metrics of resource availability, in the clear tailwater section of the Colorado River by conducting whole system metabolism measurements across a range of discharge regimes and in reaches with different orientation (i.e. N-S vs. E-W). We found that while both discharge regime and canyon orientation influence rates of primary production, seasonal changes in light availability appear to have a far stronger influence on rates of primary production in the Colorado River. Water temperature appeared to be the main driver of ecosystem respiration.

In 1974 county governments in the Atlanta vicinity realized that demands on the Chattahoochee River for water supply plus the streamflow required for water quality nearly equaled the minimum flow in the river. Increased demands for water supply in the following years could not be supplied under the then existing flow regime in the river. In response to the anticipated shortage of water, the Atlanta Regional Commission, a multicounty agency responsible for comprehensive regional planning in the Atlanta region, was contracted to prepare water demand projections to the year 2010 and identify alternatives for meeting projected water demands. The results of this study are published in an extensive final report, the Metropolitan Atlanta Area Water Resources Management Study (1981). Requests for copies should be directed to the District Engineer, Savannah District. Many of the identified alternatives to increase future water supply for the Atlanta area would result in modifications to the present flow regime within the Chattahoochee River between Buford Dam (river mile 348.3) and its confluence with Peachtree Creek (river mile 300.5). The present preferred alternative is construction of a reregulation dam at about river mile 342. The proposed reregulation dam would release a much more constant flow than the peaking flows presently released from Buford Dam (generally, a maximum release of approximately 9000 cfs or minimum release of about 550 cfs) by storing the generation releases from Buford Dam for gradual release during non-generation periods. The anticipated minimum release from the rereg dam would he approximately 1U5U cfs (based on contractual obligations to the Southeast Power Administration to supply a minimum of 11 hours of peaking power per week from Buford Dam). The average annual release from the proposed reregulation dam into the Chattahoochee River would be approximately 2000 cfs (based on USGS flow records) and the median release would he approximately 1500

Wavelet analysis is a powerful tool with which to analyse the hydrologic effects of dam construction and operation on river systems. Using continuous records of instantaneous discharge from the Lees Ferry gauging station and records of daily mean discharge from upstream tributaries, we conducted wavelet analyses of the hydrologic structure of the Colorado River in Grand Canyon. The wavelet power spectrum (WPS) of daily mean discharge provided a highly compressed and integrative picture of the post-dam elimination of pronounced annual and sub-annual flow features. The WPS of the continuous record showed the influence of diurnal and weekly power generation cycles, shifts in discharge management, and the 1996 experimental flood in the post-dam period. Normalization of the WPS by local wavelet spectra revealed the fine structure of modulation in discharge scale and amplitude and provides an extremely efficient tool with which to assess the relationships among hydrologic cycles and ecological and geomorphic systems. We extended our analysis to sections of the Snake River and showed how wavelet analysis can be used as a data mining technique. The wavelet approach is an especially promising tool with which to assess dam operation in less well-studied regions and to evaluate management attempts to reconstruct desired flow characteristics. Copyright ?? 2005 John Wiley & Sons, Ltd.

Estimates of tributary inflow by basin or area and by surface water or groundwater are presented in this report and itemized by subreaches in tabular form. Total estimated average annual tributary inflow to the Colorado River between Hoover Dam and Mexico, excluding the measured tributaries, is 96,000 acre-ft or about 1% of the 7.5 million acre-ft/yr of Colorado River water apportioned to the States in the lower Colorado River basin. About 62% of the tributary inflow originates in Arizona, 30% in California, and 8% in Nevada. Tributary inflow is a small component in the water budget for the river. Most of the quantities of unmeasured tributary inflow were estimated in previous studies and were based on mean annual precipitation for 1931-60. Because mean annual precipitation for 1951-80 did not differ significantly from that of 1931-60, these tributary inflow estimates are assumed to be valid for use in 1984. Measured average annual runoff per unit drainage area on the Bill Williams River has remained the same. Surface water inflow from unmeasured tributaries is infrequent and is not captured in surface reservoirs in any of the States; it flows to the Colorado River gaging stations. Estimates of groundwater inflow to the Colorad River valley. Average annual runoff can be used in a water budget; although in wet years, runoff may be large enough to affect the calculation of consumptive use and to be estimated from hydrographs for the Colorado River valley are based on groundwater recharge estimates in the bordering areas, which have not significantly changed through time. In most areas adjacent to the Colorado River valley, groundwater pumpage is small and pumping has not significantly affected the quantity of groundwater discharged to the Colorado River valley. In some areas where groundwater pumpage exceeds the quantity of groundwater discharge and water levels have declined, the quantity of discharge probably has decreased and groundwater inflow to the Colorado

Regulated river restoration through planned flooding involves trade-offs between aquatic and terrestrial components, between relict pre-dam and novel post-dam resources and processes, and between management of individual resources and ecosystem characteristics. We review the terrestrial (wetland and riparian) impacts of a 1274 m3/s test flood conducted by the U.S. Bureau of Reclamation in March/April 1996, which was designed to improve understanding of sediment transport and management downstream from Glen Canyon Dam in the Colorado River ecosystem. The test flood successfully restored sandbars throughout the river corridor and was timed to prevent direct impacts to species of concern. A total of 1275 endangered Kanab ambersnail (Oxyloma haydeni kanabensis) were translocated above the flood zone at Vaseys Paradise spring, and an estimated 10.7% of the total snail habitat and 7.7% of the total snail population were lost to the flood. The test flood scoured channel margin wetlands, including potential foraging habitats of endangered Southwestern Willow Flycatcher (Empidonax traillii extimus). It also buried ground-covering riparian vegetation under >1 m of fine sand but only slightly altered woody sandbar vegetation and some return-current channel marshes. Pre-flood control efforts and appropriate flood timing limited recruitment of four common nonnative perennial plant species. Slight impacts on ethnobotanical resources were detected >430 km downstream, but those plant assemblages recovered rapidly. Careful design of planned flood hydrograph shape and seasonal timing is required to mitigate terrestrial impacts during efforts to restore essential fluvial geomorphic and aquatic habitats in regulated river ecosystems.

Fish, especially migratory species, are assumed to benefit from dam removals that restore connectivity and access to upstream habitat, but few studies have evaluated this assumption. Therefore, we assessed the movement of migratory fishes in the springs of 2008 through 2010 and surveyed available habitat in the Little River, North Carolina, a tributary to the Neuse River, after three complete dam removals and one partial (notched) dam removal. We tagged migratory fishes with PIT tags at a resistance-board weir located at a dam removal site (river kilometer [rkm] 3.7) and followed their movements with an array of PIT antennas. The river-wide distribution of fish following removals varied by species. For example, 24–31% of anadromous American Shad Alosa sapidissima, 45–49% of resident Gizzard Shad Dorosoma cepedianum, and 4–11% of nonnative Flathead CatfishPylodictis olivaris passed the dam removal site at rkm 56 in 2009 and 2010. No preremoval data were available for comparison, but reach connectivity appeared to increase as tagged individuals passed former dam sites and certain individuals moved extensively both upstream and downstream. However, 17–28% did not pass the partially removed dam at rkm 7.9, while 20–39% of those that passed remained downstream for more than a day before migrating upstream. Gizzard Shad required the deepest water to pass this notched structure, followed by American Shad then Flathead Catfish. Fish that passed the notched dam accessed more complex habitat (e.g., available substrate size-classes) in the middle and upper reaches. The results provide strong support for efforts to restore currently inaccessible habitat through complete removal of derelict dams.

The Chijiawan river, located in the Hsuehshan Range in central Taiwan, is a steep, coarse-grained, mixed bedrock-alluvial channel subject to heavy monsoonal rainfall, occasional typhoons and frequent floods. In May 2011, a 15m-high check dam holding back around 200,000m3 of sediment was removed. To monitor subsequent channel response, an array of instruments were deployed prior to dam removal. Given the anticipated magnitude of sediment transport and excellent empirical constraints, the Chijiawan channel is an ideal location to study fluvial incision processes into bedrock. There is abundant bedrock exposed in the river bed downstream of the dam, and we are interested in how the pulse of sediment following dam removal will impact bedrock erosion rates. We monitor erosion using repeat high resolution laser scanning at 8 sites spread along a 3 km long reach, 2 sites upstream of the dam and 6 downstream. We scan two sites with a Konica Minolta Vivid 910 scanner (with an accuracy of 1.4mm), and the remaining sites with a Faro Photon 120 scanner (with an accuracy of 2mm). Scanning at ranges of ~1m (Vivid) to ~10m (Faro), we obtain resolutions of 1 to 3mm. Based on the system developed by Wilson and Hovius (2010), reference frames for repeat surveys consist of permanent stainless steel sockets installed in 14 cm deep holes drilled into the bedrock, combined with removable targets that screw into the sockets for scanning. Vivid data are processed and 3D models are constructed using Rapidform 2004 software. Faro data is processed using Faro's Scene software. In order to compare the high resolution scanning with more traditional low-tech monitoring methods, we have also installed two sets of concrete expansion bolts. We obtain profiles between bolts with both a contour gauge and the scanners. The high accuracy and resolution of these scanners, and the system of precise benchmarks enable us to detect extremely small amounts of erosion. By repeat scanning after individual

The water level of the navigation pools on the Mississippi River are maintained by the operation of tainter and roller gates at the locks and dams. Discharge ratings for the gates on Lock and Dam 18, at Gladstone, Illinois, were developed from current meter discharge measurements made in the forebays of the gate structures. Methodology is given to accurately compute the gate openings of the tainter gate. Discharge coefficients, in equations that express discharge as a function of tailwater head , forebay head, and height of gate opening, were determined for conditions of submerged-orifice and free-weir flow. A comparison of the rating discharges with the hydraulic model rating discharges is given for submerged orifice flow for the tainter and roller gates.

The water levels of the navigation pools on the Mississippi River are maintained by the operation of tainter and roller gates at the locks and dams. Discharge ratings for the gates on Lock and Dam 17, at New Boston, Illinois, were developed from current meter discharge measurements made in the forebays of the gate structures. Methodology is given to compute the gate openings of the tainter gates accurately. Discharge coefficients , in equations that express discharge as a function of tailwater head, forebay head, and height of gate opening, were determined for conditions of submerged orifice and free weir flow. A comparison of the rating discharges to the hydraulic-model rating discharges is given for submerged orifice flow for the tainter and roller gates.

The water levels of the navigation pools on the Mississippi River are maintained by the operation of tainter and roller gates at the locks and dams. Discharge ratings for the gates on Lock and Dam 21, at Quincy, Illinois, were developed from current meter discharge measurements made in the forebays of the gate structures. Methodology is given to compute the gate openings of the tainter gates accurately. Discharge coefficients , in equations that express discharge as a function of tailwater head, forebay head, and height of gate opening, were determined for conditions of submerged orifice and free weir flow. A comparison of the rating discharges to the hydraulic model rating discharges is given for submerged orifice flow for the tainter and roller gates.

Analyses of flow, sediment-transport, bed-topographic, and sedimentologic data suggest that before the closure of Glen Canyon Dam in 1963, the Colorado River in Marble and Grand Canyons was annually supply-limited with respect to fine sediment (i.e., sand and finer material). Furthermore, these analyses suggest that the predam river in Glen Canyon was not supply-limited to the same degree and that the degree of annual supply limitation increased near the head of Marble Canyon. The predam Colorado River in Grand Canyon displays evidence of four effects of supply limitation: (1) seasonal hysteresis in sediment concentration, (2) seasonal hysteresis in sediment grain size coupled to the seasonal hysteresis in sediment concentration, (3) production of inversely graded flood deposits, and (4) development or modification of a lag between the time of a flood peak and the time of either maximum or minimum (depending on reach geometry) bed elevation. Analyses of sediment budgets provide additional support for the interpretation that the predam river was annually supply-limited with respect to fine sediment, but it was not supply-limited with respect to fine sediment during all seasons. In the average predam year, sand would accumulate and be stored in Marble Canyon and upper Grand Canyon for 9 months of the year (from July through March) when flows were dominantly below 200-300 m3/s; this stored sand was then eroded during April through June when flows were typically higher. After closure of Glen Canyon Dam, because of the large magnitudes of the uncertainties in the sediment budget, no season of substantial sand accumulation is evident. Because most flows in the postdam river exceed 200-300 m3/s, substantial sand accumulation in the postdam river is unlikely.

shellfish collections from the low-tide beach, we suggest that it is an armored layer of cobble clasts that are not generally competent in the physical setting of the delta. Thus, the cobble low-tide terrace is very likely a geomorphological feature caused by coastal erosion of a coastal plain and delta, which in turn is related to the impacts of the dams on the Elwha River to sediment fluxes to the coast.

There are limited long-term data available on the ecological health and environmental state of the Upper St. Lawrence River (CA,US; average discharge 6,910 m3/s). Our research objective is to establish long-term remote water quality monitoring stations in the Moses-Saunders hydroelectric power dam at Massena, New York using a network of sensors. Such a placement of sensors allows for year-round monitoring of water and hence, the ability to measure at times of year and during extreme weather events that previously made monitoring infeasible. The sensor array was installed on 17 June 2014 and draws water from the penstock at a rate of 6-10 L per minute. Sensors in flow through chambers collect data on temperature, turbidity, color dissolved organic material (CDOM), phycocyanin, chlorophyll-a, and specific conductivity at one minute intervals. In combination with a hydrodynamic flow model we are able to hind-cast water movements so that the quality of water passing through the dam can be related to environmental conditions in the river upstream from the sensor array. We conducted field surveys using sensors in a ferry box on a vessel moving upstream (40 km) at a velocity providing a spatial resolution of 100 m and determined that main channel water is more homogenous than water along the shorelines (2 m isopleth) of the river, despite the high turbulence in this river. The sensor array located in the turbine unit nearest the US shore is able to discern tributary inputs for CDOM from the Oswegatchie River (discharge 40-120 m3/s), located 67 km upstream. This research is an important proof-of-concept for installing similar arrays in dams throughout the Great Lakes region and is applicable to smaller rivers containing power dams.

Understanding landscape responses to sediment supply changes constitutes a fundamental part of many problems in geomorphology, but opportunities to study such processes at field scales are rare. The phased removal of two large dams on the Elwha River, Washington, exposed 21 ± 3 million m3, or ~ 30 million tonnes (t), of sediment that had been deposited in the two former reservoirs, allowing a comprehensive investigation of watershed and coastal responses to a substantial increase in sediment supply. Here we provide a source-to-sink sediment budget of this sediment release during the first two years of the project (September 2011-September 2013) and synthesize the geomorphic changes that occurred to downstream fluvial and coastal landforms. Owing to the phased removal of each dam, the release of sediment to the river was a function of the amount of dam structure removed, the progradation of reservoir delta sediments, exposure of more cohesive lakebed sediment, and the hydrologic conditions of the river. The greatest downstream geomorphic effects were observed after water bodies of both reservoirs were fully drained and fine (silt and clay) and coarse (sand and gravel) sediments were spilling past the former dam sites. After both dams were spilling fine and coarse sediments, river suspended-sediment concentrations were commonly several thousand mg/L with ~ 50% sand during moderate and high river flow. At the same time, a sand and gravel sediment wave dispersed down the river channel, filling channel pools and floodplain channels, aggrading much of the river channel by ~ 1 m, reducing river channel sediment grain sizes by ~ 16-fold, and depositing ~ 2.2 million m3 of sand and gravel on the seafloor offshore of the river mouth. The total sediment budget during the first two years revealed that the vast majority (~ 90%) of the sediment released from the former reservoirs to the river passed through the fluvial system and was discharged to the coastal waters, where

Understanding landscape responses to sediment supply changes constitutes a fundamental part of many problems in geomorphology, but opportunities to study such processes at field scales are rare. The phased removal of two large dams on the Elwha River, Washington, exposed 21 ± 3 million m3, or ~ 30 million tonnes (t), of sediment that had been deposited in the two former reservoirs, allowing a comprehensive investigation of watershed and coastal responses to a substantial increase in sediment supply. Here we provide a source-to-sink sediment budget of this sediment release during the first two years of the project (September 2011–September 2013) and synthesize the geomorphic changes that occurred to downstream fluvial and coastal landforms. Owing to the phased removal of each dam, the release of sediment to the river was a function of the amount of dam structure removed, the progradation of reservoir delta sediments, exposure of more cohesive lakebed sediment, and the hydrologic conditions of the river. The greatest downstream geomorphic effects were observed after water bodies of both reservoirs were fully drained and fine (silt and clay) and coarse (sand and gravel) sediments were spilling past the former dam sites. After both dams were spilling fine and coarse sediments, river suspended-sediment concentrations were commonly several thousand mg/L with ~ 50% sand during moderate and high river flow. At the same time, a sand and gravel sediment wave dispersed down the river channel, filling channel pools and floodplain channels, aggrading much of the river channel by ~ 1 m, reducing river channel sediment grain sizes by ~ 16-fold, and depositing ~ 2.2 million m3 of sand and gravel on the seafloor offshore of the river mouth. The total sediment budget during the first two years revealed that the vast majority (~ 90%) of the sediment released from the former reservoirs to the river passed through the fluvial system and was discharged to the coastal

A sharp decrease in total suspended solids (TSS) concentration has occurred in the Mekong River after the closure of the Manwan Dam in China in 1993, the first of a planned cascade of eight dams. This paper describes the upstream developments on the Mekong River, concentrating on the effects of hydropower dams and reservoirs. The reservoir-related changes in total suspended solids, suspended sediment concentration (SSC), and hydrology have been analyzed, and the impacts of such possible changes on the Lower Mekong Basin discussed. The theoretical trapping efficiency of the proposed dams has been computed and the amount of sediment to be trapped in the reservoirs estimated. The reservoir trapping of sediments and the changing of natural flow patterns will impact the countries downstream in this international river basin. Both positive and negative possible effects of such impacts have been reviewed, based on the available data from the Mekong and studies on other basins.

In the first part of this work, the progress of Italian National Rules about dams design, construction and operation are presented to highlight the strong connection existing between the promulgation of new decrees, as a consequence of a dam accidents, and the necessity to prevent further loss of lives and goods downstream. Following the Gleno Dam failure (1923), a special Ministerial Committee wrote out the first Regulations and made the proposal to establish, within the High Council of Public Works, a special department that become soon the "Dam Service", with the tasks of control and supervision about construction and operation phases of the dams and their reservoirs. A different definition of tasks and the structure of Dam Service were provided in accordance with law n° 183/1989, which transferred all the technical services to the Office of the Prime Minister; the aim was to join the Dam Office with the Department for National Technical Services, with the objective of increasing the knowledge of the territory and promoting the study on flood propagation downstream in case of operations on bottom outlet or hypothetical dam-break. In fact, population living downstream is not ready to accept any amount of risk because has not a good knowledge of the efforts of experts involved in dam safety, both from the operators and from the safety Authority. So it's important to optimize all the activities usually performed in a dam safety program and improve the emergency planning as a response to people's primary needs and feeling about safety from Civil Protection Authority. In the second part of the work, a definition of risk is provided as the relationship existing between probability of occurrence and loss, setting out the range within to plan for prevention (risk mitigation), thanks to the qualitative assessment of the minimum safety level that is suited to assign funds to plan for Civil Protection (loss mitigation). The basic meaning of the reliability of a zoned

Closure of Glen Canyon Dam in 1963 transformed the Colorado River by reducing the magnitude and duration of spring floods, increasing the magnitude of base flows, and trapping fine sediment delivered from the upper watershed. These changes caused the channel downstream in Glen Canyon to incise, armor, and narrow. This study synthesizes over 45 yr of channel-change measurements and demonstrates that the rate and style of channel adjustment are directly related to both natural processes associated with sediment deficit and human decisions about dam operations. Although bed lowering in lower Glen Canyon began when the first cofferdam was installed in 1959, most incision occurred in 1965 in conjunction with 14 pulsed high flows that scoured an average of 2.6 m of sediment from the center of the channel. The average grain size of bed material has increased from 0.25 mm in 1956 to over 20 mm in 1999. The magnitude of incision at riffles decreases with distance downstream from the dam, while the magnitude of sediment evacuation from pools is spatially variable and extends farther downstream. Analysis of bed-material mobility indicates that the increase in bed-material grain size and reduction in reach-average gradient are consistent with the transformation of an adjustable-bed alluvial river to a channel with a stable bed that is rarely mobilized. Decreased magnitude of peak discharges in the post-dam regime coupled with channel incision and the associated downward shifts of stage-discharge relations have caused sandbar and terrace erosion and the transformation of previously active sandbars and gravel bars to abandoned deposits that are no longer inundated. Erosion has been concentrated in a few pre-dam terraces that eroded rapidly for brief periods and have since stabilized. The abundance of abandoned deposits decreases downstream in conjunction with decreasing magnitude of shift in the stage-discharge relations. In the downstream part of the study area where riffles

SummaryUnder the influence of climate and human activities, fluvial systems have natural ability to make adjustments so that the river hydrology, sediment movement, and channel morphology are in dynamic equilibrium. Taking the Changjiang (Yangtze River) for example. In the early stages after the Three Gorges Dam (TGD) began operational ten years ago, the suspended sediment content (SSC) and fluxes in the middle and lower reaches of the river decreased noticeably. At present, they appear to be in a stable state on the decadal scale. Although the river runoff has not shown any trends, the water level in the river decreased appreciably in time. In the meantime, channel down cutting along the thalweg almost existed throughout the river course. The riverbed has turned from depositional before the dam construction to erosional afterwards. In other words, the riverbed had turned from being sediment sinks to sediment sources. In the main channel of the Changjiang between Yichang and Nanjing, a distance of 1300 km, the riverbed sedimentation mode displays strong, intermediate, and weak erosion depending on the closeness to the TGD.

Physical changes to rivers associated with large dams (e.g., water temperature) directly alter macroinvertebrate assemblages. Large dams also may indirectly alter these assemblages by changing the food resources available to support macroinvertebrate production. We examined the diets of the 4 most common macroinvertebrate taxa in the Colorado River through Glen and Grand Canyons, seasonally, at 6 sites for 2.5 y. We compared macroinvertebrate diet composition to the composition of epilithon (rock and cliff faces) communities and suspended organic seston to evaluate the degree to which macroinvertebrate diets tracked downstream changes in resource availability. Diets contained greater proportions of algal resources in the tailwater of Glen Canyon Dam and more terrestrial-based resources at sites downstream of the 1st major tributary. As predicted, macroinvertebrate diets tracked turbidity-driven changes in resource availability, and river turbidity partially explained variability in macroinvertebrate diets. The relative proportions of resources assimilated by macroinvertebrates ranged from dominance by algae to terrestrial-based resources, despite greater assimilation efficiencies for algal than terrestrial C. Terrestrial resources were most important during high turbidity conditions, which occurred during the late-summer monsoon season (July–October) when tributaries contributed large amounts of organic matter to the mainstem and suspended sediments reduced algal production. Macroinvertebrate diets were influenced by seasonal changes in tributary inputs and turbidity, a result suggesting macroinvertebrate diets in regulated rivers may be temporally dynamic and driven by tributary inputs.

Historic land use, dam construction, water storage, and flow diversions in the Trinity River watershed have resulted in downstream geomorphic change, loss of salmonid habitat, and declines in salmonid populations. The USGS in cooperation with the Trinity River Restoration Program, a multi-agency partnership tasked with implementing federally mandated restoration, completed a geomorphic change assessment to inform the planning process for future restoration work. This report documents an ARCMAP geodatabase (v.10.0) containing geomorphic features digitized from a series of rectified orthophotographs (http://dx.doi.org/10.5066/F7TT4P04). Upland, riparian, and channel features were digitized from six available base images (1980, 1997, 2001, 2006, 2009, and 2011). This report describes the structure of the geodatabase and the methods used to delineate individual geomorphic features.

Migratory bull trout (Salvelinus confluentus) historically spawned in tributaries of the Clark Fork River, Montana and inhabited Lake Pend Oreille as subadult and adult fish. However, in 1952 Cabinet Gorge Dam was constructed without fish passage facilities disrupting the connectivity of this system. Since the construction of this dam, bull trout populations in upstream tributaries have been in decline. Each year adult bull trout return to the base of Cabinet Gorge Dam when most migratory bull trout begin their spawning migration. However, the origin of these fish is uncertain. We used eight microsatellite loci to compare bull trout collected at the base of Cabinet Gorge Dam to fish sampled from both above and further downstream from the dam. Our data indicate that Cabinet Gorge bull trout are most likely individuals that hatched in above-dam tributaries, reared in Lake Pend Oreille, and could not return to their natal tributaries to spawn. This suggests that the risk of outbreeding depression associated with passing adults over dams in the Clark Fork system is minimal compared to the potential genetic and demographic benefits to populations located above the dams. PMID:11380874

The October 2007 removal of Marmot Dam on the Sandy River, Oregon, triggered a rapid sequence of fluvial responses as ~730,000 m3 of sand and gravel that filled the former reservoir were suddenly exposed to an energetic river. Using direct measurements of sediment transport, photogrammetry, and repeat surveys between transport events, we monitored the erosion, transport, and redeposition of this sediment in the hours, days, and months following breaching. Measurements of suspended load and bedload documented an initial spike in the flux of fine suspended sediment in the minutes after breaching followed by high rates of suspendedand bedload transport of sand. Significant gravel transport did not begin at a measurement site 0.4 km downstream of the dam until 18–20 hours after breaching, when bedload transport achieved rates of about 60 kg/s—rates that greatly exceeded concurrent measurements of less than 10 kg/s at sites upstream and farther downstream of the dam. Bedload transport rates just below the dam site remained 10–100 times above upstream and downstream rates through subsequent high flow events during the winter and spring of 2007 and 2008. Much of the elevated sediment load was derived from eroded reservoir sediment, which initially began eroding when a multi-meter-tall knickpoint migrated upstream 200 meters in the first hour. Rapid knickpoint migration triggered bank collapse in the unconsolidated fill, which swiftly widened the channel. Over the following days and months, the knickpoint migrated slowly upchannel, simultaneously lowering and becoming less distinct. By May 2008, a riffle-like feature approximately 1 m high, a few tens of meters long, and 2 km upstream from the breached dam persisted. Knickpoint and lateral erosion evacuated ~100,000 cubic meters of sediment from the reservoir in the first 60 hours, and by the end of high flows in May 2008 about 350,000 cubic meters (45 percent of the initial reservoir volume) had been evacuated

Wild-spawned white sturgeon (Acipenser transmontanus) larvae captured and reared in aquaculture facilities and subsequently released, are increasingly being used in sturgeon restoration programs in the Columbia River Basin. A reconnaissance study was conducted to determine where to deploy nets to capture white sturgeon larvae downstream of a known white sturgeon spawning area. As a result of the study, 103 white sturgeon larvae and 5 newly hatched free-swimming embryos were captured at 3 of 5 reconnaissance netting sites. The netting, conducted downstream of The Dalles Dam on the Columbia River during June 25–29, 2012, provided information for potentially implementing full-scale collection efforts of large numbers of larvae for rearing in aquaculture facilities and for subsequent release at a larger size in white sturgeon restoration programs.

American shad Alosa sapidissima are in decline throughout much of their native range as a result of overfishing, pollution, and habitat alteration in coastal rivers where they spawn. One approach to restoration in regulated rivers is to provide access to historical spawning habitat above dams through a trap-and-transport program. We examined the initial survival, movement patterns, spawning, and downstream passage of sonic-tagged adult American shad transported to reservoir and riverine habitats upstream of hydroelectric dams on the Roanoke River, North Carolina and Virginia, during 2007–2009. Average survival to release in 2007–2008 was 85%, but survival decreased with increasing water temperature. Some tagged fish released in reservoirs migrated upstream to rivers; however, most meandered back and forth within the reservoir. A higher percentage of fish migrated through a smaller (8,215-ha) than a larger (20,234-ha) reservoir, suggesting that the population-level effects of transport may depend on upper basin characteristics. Transported American shad spent little time in upper basin rivers but were there when temperatures were appropriate for spawning. No American shad eggs were collected during weekly plankton sampling in upper basin rivers. The estimated initial survival of sonic-tagged American shad after downstream passage through each dam was 71–100%; however, only 1% of the detected fish migrated downstream through all three dams and many were relocated just upstream of a dam late in the season. Although adult American shad were successfully transported to upstream habitats in the Roanoke River basin, under present conditions transported individuals may have reduced effective fecundity and postspawning survival compared with nontransported fish that spawn in the lower Roanoke River.

16. Parker Dam, only top fourth of dam visible, at 320' high, Parker Dam is one of the highest in the world. Much of this height is because dam penetrates well below river bottom to fasten to bedrock. - Parker Dam, Spanning Colorado River between AZ & CA, Parker, La Paz County, AZ

The removal of two long-standing dams on the Elwha River in Washington State will initiate a suite of biological and physical changes to the estuary at the river mouth. Estuaries represent a transition between freshwater and saltwater, have unique assemblages of plants and animals, and are a critical habitat for some salmon species as they migrate to the ocean. This chapter summarizes a number of studies in the Elwha River estuary, and focuses on physical and biological aspects of the ecosystem that are expected to change following dam removal. Included are data sets that summarize (1) water chemistry samples collected over a 16 month period; (2) beach seining activities targeted toward describing the fish assemblage of the estuary and migratory patterns of juvenile salmon; (3) descriptions of the aquatic and terrestrial invertebrate communities in the estuary, which represent an important food source for juvenile fish and are important water quality indicators; and (4) the diet and growth patterns of juvenile Chinook salmon in the lower Elwha River and estuary. These data represent baseline conditions of the ecosystem after nearly a century of changes due to the dams and will be useful in monitoring the changes to the river and estuary following dam removal.

A batch of lab-based adsorption experiments were performed to investigate the arsenic (As) removal efficacy by activated alumina. Four factors including contact time, pH, initial As concentration and different coexisting ions were examined. The adsorbent made of activated alumina (AA) with particles of 2-4 mm diameter showed a high As removal efficiency and the As concentrations of the samples were below 0.05 mg/L when the hydraulic retention time (HRT) was operated above 5 min. The As concentrations of the samples could remain below 0.05 mg/L for 30 days. A series of AA adsorption dams coupled with several other supporting adsorption techniques were employed for As-contaminated river restoration. The engineering project functioned well, and the effluent As concentration was below 0.05 mg/L when the influent was between 0.2 and 0.7 mg/L, which met the discharge requirement of the Surface Water Quality Standards criteria III in China. The results demonstrated that AA adsorption dams could be applied for emergency treatments of small- or medium-sized rivers contaminated with As. PMID:25926343

Soil erosion not only involves the loss of fertile topsoil but is also coupled with sedimentation of dams, a double barrel problem in semi-arid regions where water scarcity is frequent. Due to increasing water requirements in South Africa, the Department of Water and Sanitation is planning water resource development in the Mzimvubu River Catchment, which is the only large river network in the country without a dam. Two dams are planned including a large irrigation dam and a hydropower dam. However, previous soil erosion studies indicate that large parts of the catchment is severely eroded. Previous studies, nonetheless, used mapping and modelling techniques that represent only a selection of erosion processes and provide insufficient information about the sediment yield. This study maps and models the sediment yield comprehensively by means of two approaches over a five-year timeframe between 2007 and 2012. Sediment yield contribution from sheet-rill erosion was modelled with ArcSWAT (a graphical user interface for SWAT in a GIS), whereas gully erosion contributions were estimated using time-series mapping with SPOT 5 imagery followed by gully-derived sediment yield modelling in a GIS. Integration of the sheet-rill and gully results produced a total sediment yield map, with an average of 5 300 t km-2 y-1. Importantly, the annual average sediment yield of the areas where the irrigation dam and hydropower dam will be built is around 20 000 t km-2 y-1. Without catchment rehabilitation, the life expectancy of the irrigation dam and hydropower dam could be 50 and 40 years respectively.

We report on our progress from April 2003 through March 2004 on determining the effects of mitigative measures on productivity of white sturgeon populations in the Columbia River downstream from McNary Dam, and on determining the status and habitat requirements of white sturgeon populations in the Columbia and Snake rivers upstream from McNary Dam. This is a multi-year study with many objectives requiring more than one year to complete; therefore, findings from a given year may be part of more significant findings yet to be reported.

We report on our progress from April 2004 through March 2005 on determining the effects of mitigative measures on productivity of white sturgeon populations in the Columbia River downstream from McNary Dam, and on determining the status and habitat requirements of white sturgeon populations in the Columbia and Snake rivers upstream from McNary Dam. This is a multi-year study with many objectives requiring more than one year to complete; therefore, findings from a given year may be part of more significant findings yet to be reported.

It is difficult for agencies to evaluate the impacts of the many planned dams on Sa??o Francisco River, Brazil, migratory fishes because fish migrations are poorly known. We conducted a study on zulega Prochilodus argenteus, an important commercial and recreational fish in the Sa??o Francisco River, to identify migrations and spawning areas and to determine linear home range. During two spawning seasons (2001-2003), we radio-tagged fish in three main-stem reaches downstream of Tre??s Marias Dam (TMD), located at river kilometer (rkm) 2,109. We tagged 10 fish at Tre??s Marias (TM), which is 5 km downstream of TMD; 12 fish at Pontal, which is 28 km downstream of TMD and which includes the mouth of the Abaete?? River, and 10 fish at Cilga, which is 45 km downstream of TMD. Late-stage (ripe) adults tagged in each area during the spawning season remained at or near the tagging site, except for four Cilga fish that went to Pontal and probably spawned. The Pontal area at the Abaete?? River mouth was the most important spawning site we found. Prespawning fish moved back and forth between main-stem staging areas upstream of the Abaete?? River mouth and Pontal for short visits. These multiple visits were probably needed as ripe fish waited for spawning cues from a flooding Abaete?? River. Some fish homed to prespaw ning staging areas, spawning areas, and nonspawning areas. The migratory style of zulega was dualistic, with resident and migratory fish. Total linear home range was also dualistic, with small (<26-km) and large (53-127-km) ranges. The locations of spawning areas and home ranges suggest that the Pontal group (which includes Cilga fish) is one population that occupies about 110 km. The Pontal population overlaps a short distance with a population located downstream of Cilga. Movements of late-stage TM adults suggest that the TM group is a separate population, possibly with connections to populations upstream of TMD. ?? Copyright by the American Fisheries Society

Few studies have evaluated survival of juvenile salmon over long river reaches in the Columbia River and information regarding the survival of sockeye salmon at lower Columbia Riverdams is lacking. To address these information gaps, the U.S. Geological Survey was contracted by the U.S. Army Corps of Engineers to evaluate the possibility of using tagged fish released in the Mid-Columbia River to assess passage and survival at and downstream of McNary Dam. Using the acoustic telemetry systems already in place for a passage and survival study at McNary Dam, fish released from the tailraces of Wells, Rocky Reach, Rock Island, Wanapum, and Priest Rapids Dams were detected at McNary Dam and at the subsequent downstream arrays. These data were used to generate route-specific survival probabilities using single-release models from fish released in the Mid-Columbia River. We document trends in passage and survival probabilities at McNary Dam for yearling Chinook and sockeye salmon and juvenile steelhead released during studies in the Mid-Columbia River. Trends in the survival and passage of these juvenile salmonid species are presented and discussed. However, comparisons made across years and between study groups are not possible because of differences in the source of the test fish, the type of acoustic tags used, the absence of the use of passive integrated transponder tags in some of the release groups, differences in tagging and release protocols, annual differences in dam operations and configurations, differences in how the survival models were constructed (that is, number of routes that could be estimated given the number of fish detected), and the number and length of reaches included in the analysis (downstream reach length and arrays). Despite these differences, the data we present offer a unique opportunity to examine the migration behavior and survival of a group of fish that otherwise would not be studied. This is particularly true for sockeye salmon because

The effects of land and water management practices (LWMP)--such as the construction of dams and roads--on river flows typically have been studied at the scale of single river watersheds or for a single type of LWMP. For the most part, assessments of the relative effects of multiple LWMP within many river watersheds across regional and national scales have been lacking. This study assesses flow alteration--quantified as deviation of several flow metrics from natural conditions--at 4196 gauged rivers affected by a variety of LWMP across the conterminous United States. The most widespread causes of flow changes among the LWMP considered were road density and dams. Agricultural development and wastewater discharges also were associated with flow changes in some regions. Dams generally reduced most attributes of flow, whereas road density, agriculture and wastewater discharges tended to be associated with increased flows compared to their natural condition. PMID:23827362

The effects of land and water management practices (LWMP)—such as the construction of dams and roads—on river flows typically have been studied at the scale of single river watersheds or for a single type of LWMP. For the most part, assessments of the relative effects of multiple LWMP within many river watersheds across regional and national scales have been lacking. This study assesses flow alteration—quantified as deviation of several flow metrics from natural conditions—at 4196 gauged rivers affected by a variety of LWMP across the conterminous United States. The most widespread causes of flow changes among the LWMP considered were road density and dams. Agricultural development and wastewater discharges also were associated with flow changes in some regions. Dams generally reduced most attributes of flow, whereas road density, agriculture and wastewater discharges tended to be associated with increased flows compared to their natural condition.

The morphological impact of river below dams due to such reservoir desiltation operation was considered and Shihmen reservoir was adopted to discuss such issue due to the new sediment venting tunnel was implemented from 2013 in this study. The Shihmen reservoir had a natural drainage area of 762.4 km2 and located at the northern Taiwan. Due to serious sediment deposition problem from 2004 induced by Typhoon AERE, the stratified withdraw facility was built at dam site to avoid the lack of public water and the one of venting tunnel of power plant was designed to vent turbidity current (Fig. 1(a)). In 2013, the sediment venting tunnel was first operated during Typhoon Soulik and abundant sediment was released to the downstream river. The 2D numerical model with sediment transport consideration was adopted to investigate morphological impact of downstream river, especially at Jiangzicui area in Fig. 1(b). Due to ecological wet land, flood diversion work and ferry boat transportation were concentrated in this area, the sediment transportation and morphological impact is important to be realized. The Fig. 1(b) shows the original morphological bed form before sediment releasing from sediment venting tunnel and Fig. 1(c) shows the simulation results after sediment releasing from sediment venting. It seems 0.2 m morphological changing due to this operation. Fig. 1(d) is the field morphological survey after Typhoon Soulik and comparison to Fig. 1 (b), not significantly deposition or erosion is observed. According to the grain size of released sediment from Shihmen reservoir, d50 is approximately 10 μm and it is belonged to fine sediment. Therefore, the released sediment is classified clay and for the morphological impact is not significantly. So, morphological impact of downstream river below Shihmen dam due to reservoir desiltation operation is unapparent after Typhoon Soulik at Jiangzicui area. Keywords: venting tunnel, turbid current, morphological impact, 2D numerical

Computer model simulations were run to determine the effects of dam removal on water temperatures along the Klamath River, located in south-central Oregon and northern California, using flow requirements defined in the 2010 Biological Opinion of the National Marine Fisheries Service. A one-dimensional, daily averaged water temperature model (River Basin Model-10) developed by the U.S. Environmental Protection Agency Region 10, Seattle, Washington, was used in the analysis. This model had earlier been configured and calibrated for the Klamath River by the U.S. Geological Survey for the U.S. Department of the Interior, Klamath Secretarial Determination to simulate the effects of dam removal on water temperatures for current (2011) and future climate change scenarios. The analysis for this report was performed outside of the scope of the Klamath Secretarial Determination process at the request of the Bureau of Reclamation Technical Services Office, Denver, Colorado.For this analysis, two dam scenarios were simulated: “dams in” and “dams out.” In the “dams in” scenario, existing dams in the Klamath River were kept in place. In the “dams out” scenario, the river was modeled as a natural stream, without the J.C. Boyle, Copco1, Copco2, and Iron Gate Dams, for the entire simulation period. Output from the two dam scenario simulations included daily water temperatures simulated at 29 locations for a 50-year period along the Klamath River between river mile 253 (downstream of Link RiverDam) and the Pacific Ocean. Both simulations used identical flow requirements, formulated in the 2010 Biological Opinion, and identical climate conditions based on the period 1961–2009.Simulated water temperatures from January through June at almost all locations between J.C. Boyle Reservoir and the Pacific Ocean were higher for the “dams out” scenario than for the “dams in” scenario. The simulated mean monthly water temperature increase was highest [1.7–2

This is a study of the scientific component of an effort to restore an urban river by removing a low-head dam. The Secor Dam is owned by a local government entity near Toledo, Ohio. The proposed removal of the last structure impeding flow on the Ottawa River has broad appeal, but the owner is concerned about liability issues, particularly potential changes to the flood regime, the presence of contaminated sediments behind the dam, and possible downstream transport of reservoir sediments. Assessing sediment contamination involved sediment sampling and analysis of trace metals and organic contaminants. Forecasting sediment transport involved field methods to determine the volume and textural properties of reservoir and upstream sediment and calculations to determine the fate of reservoir sediments. Forecasting changes in the flood regime involved HEC-RAS hydrological models to determine before and after dam removal flood scenarios using LiDAR data imported into an ArcGIS database. The resulting assessment found potential sediment contamination to be minor, and modeling showed that the removal of the dam would have minimal impacts on sediment transport and flood hazards. Based on the assessment, the removal of the dam has been approved by its owners. PMID:17122999

Condit Dam is one of the largest hydroelectric dams ever removed in the USA. Breached in a single explosive event in October 2011, hundreds-of-thousands of cubic metres of sediment washed down the White Salmon River onto spawning grounds of a threatened species, Columbia River tule fall Chinook salmon Oncorhynchus tshawytscha. We investigated over a 3-year period (2010–2012) how dam breaching affected channel morphology, river hydraulics, sediment composition and tule fall Chinook salmon (hereafter ‘tule salmon’) spawning habitat in the lower 1.7 km of the White Salmon River (project area). As expected, dam breaching dramatically affected channel morphology and spawning habitat due to a large load of sediment released from Northwestern Lake. Forty-two per cent of the project area that was previously covered in water was converted into islands or new shoreline, while a large pool near the mouth filled with sediments and a delta formed at the mouth. A two-dimensional hydrodynamic model revealed that pool area decreased 68.7% in the project area, while glides and riffles increased 659% and 530%, respectively. A spatially explicit habitat model found the mean probability of spawning habitat increased 46.2% after dam breaching due to an increase in glides and riffles. Shifting channels and bank instability continue to negatively affect some spawning habitat as sediments continue to wash downstream from former Northwestern Lake, but 300 m of new spawning habitat (river kilometre 0.6 to 0.9) that formed immediately post-breach has persisted into 2015. Less than 10% of tule salmon have spawned upstream of the former dam site to date, but the run sizes appear healthy and stable. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

The Penobscot River Restoration Project aims to improve aquatic connectivity in New England's second largest watershed ( 22,000 km2) by removing the two lowermost, mainstem dams and bypassing a third dam on a principal tributary upstream. Project objectives include: restoring unobstructed access to the entire historic riverine range for five lower river diadromous species including Atlantic and shortnose sturgeon; significantly improving access to upstream habitat for six upper river diadromous species including Atlantic salmon; reconnecting trophic linkages between headwater areas and the Gulf of Maine; restoring fluvial processes to the former impoundments; improving recreational and Penobscot Nation cultural opportunities; and maintaining basin-wide hydropower output. The project is expected to have landscape-scale benefits and the need for a significant investment in long-term monitoring and evaluation to formally quantify ecosystem response has been recognized. A diverse group of federal, state, tribal, NGO, and academic partners has developed a long-term monitoring and evaluation program composed of nine studies that began in 2009. Including American Recovery and Reinvestment Act (ARRA) funding that leveraged partner contributions, we have invested nearly $2M to date in pre- and post-removal investigations that evaluate geomorphology/bed sediment, water quality, wetlands, and fisheries. Given the number of affected diadromous species and the diversity of their life histories, we have initiated six distinct, but related, fisheries investigations to document these expected changes: Atlantic salmon upstream and downstream passage efficiency using passive integrated transponder (PIT) and acoustic telemetry; fish community structure via an index of biotic integrity (IBI); total diadromous fish biomass through hydroacoustics; shortnose sturgeon spawning and habitat use via active and passive acoustic telemetry; and freshwater-marine food web interactions by

Proposed construction of a series of locks and dams in the Red River in Louisiana will cause a permanent increase in average river stage. The potentiometric surface of the shallow alluvial aquifer and the water table in the fine-grained material confining the aquifer will be affected. The purpose of this study, using digital-modeling techniques, was to predict the average postconstruction potentiometric surface (steady state) and the water table (nonsteady state) so that potential effects of the water-level changes could be evaluated. Plans for lock and dam 5 at mile 243 (kilometer 390) above the mouth of the Red River call for a pool elevation of 145 feet (44 meters) and will cause an average increase in river stage of 23 feet (7.0 meters). As a result, ground-water levels in the pool area will be raised to near land surface in much of the area between the river and Bayou Pierre and as much as 2 miles (3.2 kilometers) east of the river from the dam upstream to realined mile 220 (kilometer 350). Areas of Barksdale Air Force Base where levels are now near land surface would be enlarged and extend downstream along Flat River to near Curtis. The potentiometric surface may be above land surface near Howard, Anderson Island, and Dixie Gardens. (Woodard-USGS)

The US Army Engineer District, Nashville (ORN), regulates flows in the Cumberland River at Wolf Creek Dam to provide for hydropower generation and flood control. The ORN is considering uprating the Wolf Creek Dam powerhouse to meet future demands for power in the region by replacing existing turbines with new units having higher capacity. With the proposed new units, maximum hydropower discharge will increase with a concomitant decrease in duration of generation. This report describes and quantifies the effects of hydropower uprating on downstream habitat of adult rainbow trout, juvenile brown trout, and adult brown trout using Instream Flow Incremental Methodology concepts. The relative downstream habitat impacts of hydropower uprate are assessed by contrasting existing and uprate release schedules under the following three hydrologic conditions: low flow (90% exceedance), average flow (50% exceedance), and high flow (10% exceedance). In general, predicted habitat availability for adult rainbow trout and adult brown trout decreases under uprate release schedules for low- and average-flow hydrologic conditions. Under high-flow conditions, habitat availability for the adult-life stages increases. Habitat for juvenile brown trout is generally negligible under both existing and uprate release schedules, and consistent patterns were not observed.

Despite extensive management and research, populations of American Shad Alosa sapidissima have experienced prolonged declines, and uncertainty about the underlying mechanisms causing these declines remains. In the springs of 2007 through 2010, we used a resistance board weir and PIT technology to capture, tag, and track American Shad in the Little River, North Carolina, a tributary to the Neuse River with complete and partial removals of low-head dams. Our objectives were to examine migratory behaviors and estimate weight loss, survival, and abundance during each spawning season. Males typically immigrated earlier than females and also used upstream habitat at a higher percentage, but otherwise exhibited relatively similar migratory patterns. Proportional weight loss displayed a strong positive relationship with both cumulative water temperature during residence time and number of days spent upstream, and to a lesser extent, minimum distance the fish traveled in the river. Surviving emigrating males lost up to 30% of their initial weight and females lost up to 50% of their initial weight, indicating there are potential survival thresholds. Survival for the spawning season was low and estimates ranged from 0.07 to 0.17; no distinct factors (e.g., sex, size, migration distance) that could contribute to survival were detected. Sampled and estimated American Shad abundance increased from 2007 through 2009, but was lower in 2010. Our study provides substantial new information about American Shad spawning that may aid restoration efforts.

The river behavior downstream of dams may be strongly modified in terms of morphology, sediment transport and hydrodynamics. Over the last decades, a reduction on the supply of bed load sediments has been observed in these reaches in several alpine rivers. The main effects resulting from the reduction of sediment supply are bed armoring, river incision and bank instability which can affect negatively the aquatic ecosystem. Artificial river replenishment is one of the proposed technique to mitigate the problem of sediment deficit downstream dams and to restore the sediment continuum along these rivers. Many field experiments were performed in Japan and United States and, more recently, also in Europe. Generally, the full erosion of the replenished volumes was rarely observed and the distance travelled by the sediments in the downstream direction was often not sufficient to reestablish natural morphological conditions. In order to improve the practical applicability of replenishment technique a series of laboratory tests are performed with the purpose to investigate the hydrodynamics of the river flow once artificial replenishment is performed. Erodible volumes, reproducing sediment replenishments, are positioned along the banks of an experimental channel. A 15 m long and 2.5 m flume is used to implement two parallel test channels with trapezoidal cross section with a 0.4 m bed width and 2:3 (V:H) of bank slope. Different geometrical combinations of erodible replenishment, in terms of length, distance between volumes and position along the banks, are tested in the experimental flume. For the replenished volumes colored gravel is used which allows the visual tracking of the temporal evolution of the erosion by means of image analysis. The bed morphology is measured at the beginning and end of the tests by a high definition laser scanner. The influence of discharge is evaluated considering different submergence conditions of the replenishment volumes. The first results

Detroit Dam was constructed in 1953 on the North Santiam River in western Oregon and resulted in the formation of Detroit Lake. With a full-pool storage volume of 455,100 acre-feet and a dam height of 463 feet, Detroit Lake is one of the largest and most important reservoirs in the Willamette River basin in terms of power generation, recreation, and water storage and releases. The U.S. Army Corps of Engineers operates Detroit Dam as part of a system of 13 reservoirs in the Willamette Project to meet multiple goals, which include flood-damage protection, power generation, downstream navigation, recreation, and irrigation. A distinct cycle in water temperature occurs in Detroit Lake as spring and summer heating through solar radiation creates a warm layer of water near the surface and isolates cold water below. Controlling the temperature of releases from Detroit Dam, therefore, is highly dependent on the location, characteristics, and usage of the dam's outlet structures. Prior to operational changes in 2007, Detroit Dam had a well-documented effect on downstream water temperature that was problematic for endangered salmonid fish species, releasing water that was too cold in midsummer and too warm in autumn. This unnatural seasonal temperature pattern caused problems in the timing of fish migration, spawning, and emergence. In this study, an existing calibrated 2-dimensional hydrodynamic water-quality model [CE-QUAL-W2] of Detroit Lake was used to determine how changes in dam operation or changes to the structural release points of Detroit Dam might affect downstream water temperatures under a range of historical hydrologic and meteorological conditions. The results from a subset of the Detroit Lake model scenarios then were used as forcing conditions for downstream CE-QUAL-W2 models of Big Cliff Reservoir (the small reregulating reservoir just downstream of Detroit Dam) and the North Santiam and Santiam Rivers. Many combinations of environmental, operational, and

The U.S. Army Engineer District, Nashville regulates flows in the Cumberland River at Wolf Creek Dam to provide for hydropower generation and flood control. To meet future demands for power in the region, the ORN is considering optimizing the generating capability at Wolf Creek Dam by both uprating existing turbines and adding more generating capability. Reregulation of the increased releases from Wolf Creek Dam is under consideration to alleviate the flow fluctuations associated with the upgrade. This report describes and quantifies the effects on trout habitat of hydropower modification and peaking operation at Wolf Creek Dam on trout habitat in the reach of the Cumberland River between Wolf Creek Dam and the site of the reregulation dam both with and without reregulation. The results of this comparison indicate that reregulation will generally have a beneficial impact on trout habitat, primarily because the backwater effects caused by the reregulation dam reduce the water velocities associated with peak discharge.

The Mississippi Delta is presently undergoing a catastrophic drowning, whereby 5000 km2 of low-lying wetlands have converted to open water. This land loss is primarily the result of: a) relative sea-level rise, occurring due to the combined effect of rapid subsidence associated with subsurface fluids extraction and eustatic rise; b) leveeing and damming of the river and its tributaries, which restricts sediment delivery to and dispersal within the delta; and c) severe excavation of the delta for navigation channels. It has been argued that continued net land loss of the Mississippi Delta is inevitable due to declining measured total (sand and mud) suspended sediment loads over the past 6 decades. However, recent research has documented that the key to delta growth is deposition of sand, which accounts for ~50-70% of modern and ancient (up to 9 m.a.) Mississippi Delta deposits, but comprises only ~20% of the sampled portion of the total load. Here we present new analysis of existing data to show that sand transport has not diminished since dam construction. Furthermore, we produce a numerical model based on the mass balance of bed material loads over the lower 1600 km of the Mississippi River to show that mining of sand from the channel bed continues to replenish downstream sand loads. For example, our model results indicate that it requires approximately 240 years for a reduced sand load to reach the delta apex. Furthermore, our calculations indicate that sand load at the delta apex is reduced by a noticeable amount (17%) only after about 600 years. We also show how channel bed elevations are predicted to change over the lower 1600 km of the river channel due to channel mining. Channel-bed degradation is greatest at the upstream end of the study reach and decreases downstream. After 300 years the wave of significant degradation has just passed ~800 km downstream, or roughly half of our model domain. These results are in contrast to the measurements which concern

In 2011 a multi-year deconstruction of two long-standing, high-head dams began on the Elwha River, Washington State. Over the past decade, we have been monitoring a variety of ecosystem attributes in the Elwha River basin to establish baseline conditions prior to one of the largest watershed restoration projects in the US. Our study design is tailored to the Elwha's geomorphic template, as different channel types are expected to respond differently to the large amount of sediment that will be released. A primary focus of this effort has been on the 28 km of floodplain channels below the dams (for every 1km of main stem habitat there is 1.35km of floodplain channel). Another focus has been on main stem channel features such as pool and riffle habitat, which are critical habitats for salmonids and other biota. How will these floodplain channels and mainstem channel features react to the large amount of sediment that is being released? We have used simple field techniques such as longitudinal profiles of floodplain channels, pebble counts, turbidity measurements, and the amount of sediment accumulation in pools and riffles to document baseline as well as "during dam removal" conditions. Early results indicate increased turbidity downstream of dams throughout deconstruction, suggesting there will be dramatic increases in fine sediment accumulations once dam removal is completed. We plan to continue using inexpensive methods to quantify the geomorphic and ecological change following dam removal in the Elwha River basin. These findings have direct implications for other dam removal projects.

...The Coast Guard will enforce a segment of the Safety Zone; Brandon Road Lock and Dam to Lake Michigan including Des Plaines River, Chicago Sanitary and Ship Canal, Chicago River, Calumet-Saganashkee Channel on all waters of the Chicago Sanitary and Ship Canal from Mile Marker 296.1 to Mile Marker 296.7 at various times from June 14, 2012 until June 22, 2012. This action is necessary to protect......

...The Coast Guard will enforce a segment of the Safety Zone; Brandon Road Lock and Dam to Lake Michigan including Des Plaines River, Chicago Sanitary and Ship Canal, Chicago River, Calumet-Saganashkee Channel on all waters of the Chicago Sanitary and Ship Canal from Mile Marker 296.1 to Mile Marker 296.7 at specified times on each day from November 4 through November 8, and again on November 13,......

...The Coast Guard will enforce a segment of the Safety Zone; Brandon Road Lock and Dam to Lake Michigan including Des Plaines River, Chicago Sanitary and Ship Canal, Chicago River, Calumet-Saganashkee Channel on all waters of the Chicago Sanitary and Ship Canal from Mile Marker 296.1 to Mile Marker 296.7 at various times on each day from June 17 through June 21, 2013. This action is necessary to......

...The Coast Guard will enforce a segment of the Safety Zone; Brandon Road Lock and Dam to Lake Michigan including Des Plaines River, Chicago Sanitary and Ship Canal, Chicago River, Calumet-Saganashkee Channel on all waters of the Chicago Sanitary and Ship Canal from Mile Marker 296.1 to Mile Marker 296.7 at specified times on each day from August 12 through August 16, 2013. This action is......

...The Coast Guard will enforce a segment of the Safety Zone; Brandon Road Lock and Dam to Lake Michigan including Des Plaines River, Chicago Ship and Sanitary Canal, Chicago River, Calumet-Saganashkee Channel on all waters of the Chicago Sanitary and Ship Canal between Mile Marker 291.0 and Mile Marker 296.1 from 4 p.m. on October 19, 2010 to 12 p.m. on October 20, 2010 and from 4 p.m. on......

Epilithic community metabolism was determined on a seasonal basis over two years in nonregulated and regulated reaches of the Clearwater River in northern Idaho, U.S.A. Metabolism was estimated using three, 12-liter recirculating chambers and the dissolved oxygen method, with parameters expressed as g O2 m−2 d−1. In the nonregulated reach above the reservoir, gross community productivity (GCP) ranged from 0.8 to 3.2, community respiration (CR24) from 0.3 to 1.2, and production/respiration (P/R) ratios from 1.2 to 3.3. Epilithic metabolism in the regulated reach immediately below the dam increased sharply; GCP ranged from 4.2 to 25.5, CR24 from 1.9 to 9.7, and P/R ratios from 1.4 to 5.7. Increased primary production and respiration in the regulated reach was a result of extensive growth of an aquatic moss (Fontanalis neo-mexicanus). The influence of the dam on epilithic community metabolism was mitigated 2.5 km downstream of the dam due to the regulated North Fork of the Clearwater River (NFCR) merging with the larger, nonregulated Clearwater River. While the regulated Clearwater River below the confluence was somewhat affected by the regulated NFCR flows upstream, metabolism was similar to that found above the reservoir (GCP = 1.2 – 2.6, CR24 = 0.6 – 1.3, and P/R = 1.4 – 2.2). This study demonstrates that while Dworshak Dam has altered both primary production and respiration directly below the dam, the placement of the dam only 2.5 km upstream from a nonregulated reach greatly mitigates its effects on stream metabolism downstream.

The Elwha Riverdams have disconnected the upper and lower Elwha watershed for over 90 years. This has resulted in a disruption to upstream salmonid migration and a 'loss' of 90% of the salmonid habitat. The dams have also interrupted the downstream movement of both sediment and wood, leading to such inputs being dominated by local sources (e.g., bank erosion and avulsions). The current salmon habitat, as well as salmonid abundance and distribution, reflects these changes. Current salmonid populations (several of which are hatchery-dominated) are either dramatically smaller than estimated historical population or extirpated. Nevertheless, salmonid populations do persist below the dams in part because channel incision has not been significant, and floodplain habitats remain an important component of the Elwha River ecosystem. Impending removal of these dams presents an opportunity to explore linkages among changes in salmonid populations, sediment supply, in-channel wood abundance, and habitat and ecosystem attributes. Sampling of ecosystem attributes before and after dam removal, as well as in nearby reference rivers will elucidate functional relationships among salmonid populations, sediment and wood supply, formation and persistence of river and floodplain habitats, and resultant ecosystem dynamics. Dam removal will (1) reconnect upstream habitats increasing salmonid carrying capacity, and (2) allow the downstream movement of sediment and wood leading to long-term aquatic habitat improvements. Both large-scale changes will allow salmonid populations to rebuild on a watershed-scale. We hypothesize that the salmonid recolonization will be concentrated in several large alluvial valleys in the Middle and Upper Elwha.

White sturgeon (Acipenser transmontanus) ???95 cm TL were monitored using acoustic and radio telemetry at a large hydroelectric dam (the Dalles Dam) on the Columbia River, during March 2004 through November 2005 to determine timing and routes of passage and to characterize general movements. Transmitters were surgically implanted into 148 fish during the study; 90 were released into the tailrace and 58 into the forebay. We documented 26 passage events by 19 tagged fish: eight upstream via fish ladders and 18 downstream, mostly through open spill gates. During the study 17 fish entered the two ladders one or more times; 11 entered only the east ladder, three entered only the north ladder, and three entered both ladders at sometime. Residence time within the ladders by individual fish was variable, ranging from about 1 min to nearly 6 months (median = 7.7 h). Only six fish successfully ascended the east ladder, one fish twice. We could not unequivocally determine which fish ladder one fish used to pass upstream. Differences in construction between the north and east fish ladders may account for the greater success of the east fish ladder in passing sturgeon upstream. Changes to operations at hydroelectric dams to benefit migrating anadromous salmonids may influence upstream or downstream passage by white sturgeon. Altering patterns and timing of spill discharge, altering fish ladder entrance attraction flows, and the use of lights, sound, and partial barriers to direct other species of fish to preferred passage routes have unknown effects on sturgeon passage. A better understanding of the consequences to the metapopulation of increasing or precluding upstream or downstream passage is needed. ?? 2007 The Authors.

We conclude that most of the river-corridor archeological sites are at elevated risk of net erosion under present dam operations. In the present flow regime, controlled floods do not simulate the magnitude or frequency of natural floods, and are not large enough to deposit sand at elevations that were flooded at annual to decadal inte

Water temperature is an important factor influencing the migration, rearing, and spawning of several important fish species in rivers of the Pacific Northwest. To protect these fish populations and to fulfill its responsibilities under the Federal Clean Water Act, the Oregon Department of Environmental Quality set a water temperature Total Maximum Daily Load (TMDL) in 2006 for the Willamette River and the lower reaches of its largest tributaries in northwestern Oregon. As a result, the thermal discharges of the largest point sources of heat to the Willamette River now are limited at certain times of the year, riparian vegetation has been targeted for restoration, and upstream dams are recognized as important influences on downstream temperatures. Many of the prescribed point-source heat-load allocations are sufficiently restrictive that management agencies may need to expend considerable resources to meet those allocations. Trading heat allocations among point-source dischargers may be a more economical and efficient means of meeting the cumulative point-source temperature limits set by the TMDL. The cumulative nature of these limits, however, precludes simple one-to-one trades of heat from one point source to another; a more detailed spatial analysis is needed. In this investigation, the flow and temperature models that formed the basis of the Willamette temperature TMDL were used to determine a spatially indexed 'heating signature' for each of the modeled point sources, and those signatures then were combined into a user-friendly, spreadsheet-based screening tool. The Willamette River Point-Source Heat-Trading Tool allows the user to increase or decrease the heating signature of each source and thereby evaluate the effects of a wide range of potential point-source heat trades. The predictions of the Trading Tool were verified by running the Willamette flow and temperature models under four different trading scenarios, and the predictions typically were accurate

While most large river-deltas in the world are facing the risk of subsidence and erosion in the Anthropocene, it is suspected that the Changjiang submerged delta (CSD) could be subjected to the impacts of the world's largest dam, the Three Gorges Dam (TGD). Here we firstly indicate that the CSD went through high accumulation (1958-1978); slight accumulation (1978-1997), slight erosion (1997-2002); and high accumulation (2002-2009), despite the 70% reduction of the sediment load from upstream since the operation of the TGD in 2003. Meanwhile, at the depocenter of the submerged delta, the accumulation maintained a high rate of 10 cm/yr during 1958-2009. This suggests on a longer term, the distal sediment source from the upstream had little effect on the CSD. Within this time frame the changes in the partition of sediment load among the branching channels of the Changjiang Estuary could likely control the shifting of the depocenter of the CSD on a decadal time scale. Episodic extreme floods and storm surges also increased the magnitude of deposition and erosion of the CSD on short-term scales. A re-evaluation of the impacts of TGD on the CSD is urgently needed. PMID:25321660

While most large river-deltas in the world are facing the risk of subsidence and erosion in the Anthropocene, it is suspected that the Changjiang submerged delta (CSD) could be subjected to the impacts of the world's largest dam, the Three Gorges Dam (TGD). Here we firstly indicate that the CSD went through high accumulation (1958-1978) slight accumulation (1978-1997), slight erosion (1997-2002) and high accumulation (2002-2009), despite the 70% reduction of the sediment load from upstream since the operation of the TGD in 2003. Meanwhile, at the depocenter of the submerged delta, the accumulation maintained a high rate of 10 cm/yr during 1958-2009. This suggests on a longer term, the distal sediment source from the upstream had little effect on the CSD. Within this time frame the changes in the partition of sediment load among the branching channels of the Changjiang Estuary could likely control the shifting of the depocenter of the CSD on a decadal time scale. Episodic extreme floods and storm surges also increased the magnitude of deposition and erosion of the CSD on short-term scales. A re-evaluation of the impacts of TGD on the CSD is urgently needed.

A proposed methodology is based on estimated groundwater volumes from tritium river water measurements in the Ishikari River basin of Hokkaido Island, Japan. In our drought assessment, we characterize a groundwater storage that is available and can be used for the water supply during prolonged droughts. For the groundwater storage estimation, we utilized tritium river water measurements obtained during baseflows to estimate water mean transit times (MTTs). Tritium is ideally suited for characterization of the catchment's responses in river water samples with MTTs times up to 200 years. Tritium is a component of meteoric water, decays with a half-life of 12.32 years, and is inert in the subsurface. In Hokkaido, river water samples were collected in June, July and October 2014 at selected river gauging stations operated by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT). These stations record hourly water levels, have catchment areas between 45 and 377 km2 and are located upstream of MLIT dams at altitudes between 36 m and 860 m MSL. The measured tritium ranged between 4.065 TU (±0.07) and 5.290 TU (±0.09) with both lowest and highest tritium values analysed in June river samples at Tougeshita and Okukatsura stations, respectively. For the MTT estimation, we selected exponential(80%)-piston(20%) Lumped Parameter Model (LPM) with constructed tritium in Hokkaido precipitation and obtained a non-unique fit of young (1-11 years) and old (16-98 years) groundwater MTTs. This result indicates that the bomb-peak tritium is still present in Japanese groundwater and may take several years to flush out. From the MTTs and baseflow discharges, the calculated groundwater volume ranges between 13 MCM and 12500 MCM and indicates potentially available groundwater storage during prolonged droughts in the Hokkaido headwater catchments. In the future studies, the accuracy of the estimated groundwater volume can be increased by conducting another tritium sampling at

Simple and reliable methods for estimating hourly streamflow are needed for the calibration and verification of a Chattahoochee River basin model between Buford Dam and Franklin, Ga. The river basin model is being developed by Georgia Department of Natural Resources, Environmental Protection Division, as part of their Chattahoochee River Modeling Project. Concurrent streamflow data collected at 19 continuous-record, and 31 partial-record streamflow stations, were used in ordinary least-squares linear regression analyses to define estimating equations, and in verifying drainage-area prorations. The resulting regression or drainage-area ratio estimating equations were used to compute hourly streamflow at the partial-record stations. The coefficients of determination (r-squared values) for the regression estimating equations ranged from 0.90 to 0.99. Observed and estimated hourly and daily streamflow data were computed for May 1, 1995, through October 31, 1995. Comparisons of observed and estimated daily streamflow data for 12 continuous-record tributary stations, that had available streamflow data for all or part of the period from May 1, 1995, to October 31, 1995, indicate that the mean error of estimate for the daily streamflow was about 25 percent.

This report contains water-quality data for the Ohio River from river mile 51.1 (3.3 miles upstream from New Cumberland Dam) to river mile 84.0 (0.2 miles upstream from Pike Island Dam) that were collected during the summer and fall of 1993. The data were collected to establish the water quality of the Ohio River and to use in assessing the proposed effects of hydropower development on the water quality of the Ohio River. Water quality was determined by a combination of repeated synoptic field measurements, continuous-record monitoring, and laboratory analyses. Synoptic measurements were made along a longitudinal transect with 18 mid-channel sampling sites; cross-sectional transects of water-quality measurements were made at 5 of these sites. Water-quality measurements also were made at two sites located on the back-channel (Ohio) side of Browns Island. At each longitudinal-transect and back-channel sampling site, measurements were made of specific conductance, pH, water temperature, and dissolved oxygen conentration. Longitudinal-transect and back-channel stations were sampled at four depths (at the surface, about 3.3 feet below the surface, middle of the water column, and near the bottom of the river). Cross-sectional transects consisted of three to four detailed vertical profiles of the same characteristics. Water samples were collected from three depths at the mid-channel vertical profile in each cross-sectional transect and were analyzed for concentrations of phytoplankton photosynthetic pigments chlorophyll a and chlorophyll b. Estimates of the depth of light penetration (Secchi-disk transparency) were made at pigment-sampling locations whenever light and river-surface conditions were appropriate. Synoptic sampling usually was completed in 12 hours or less and was repeated 10 times from May through October 1993. Continuous-record monitoring of water quality consisted of hourly measurements of specific conductance, pH, water temperature, and dissolved oxygen

Monitoring of dam passage can be useful for management and conservation assessments of American eel, particularly if passage counts can be examined over multiple years. During a 7-year study (2007–2013) of upstream migration of American eels within the lower Shenandoah River (Potomac River drainage), we counted and measured American eels at the Millville Dam eel pass, where annual study periods were determined by the timing of the eel pass installation during spring or summer and removal during fall. Daily American eel counts were analysed with negative binomial regression models, with and without a year (YR) effect, and with the following time-varying environmental covariates: river discharge of the Shenandoah River at Millville (RDM) and of the Potomac River at Point of Rocks, lunar illumination (LI), water temperature, and cloud cover. A total of 17 161 yellow-phase American eels used the pass during the seven annual periods, and length measurements were obtained from 9213 individuals (mean = 294 mm TL, s.e. = 0.49, range 183–594 mm). Data on passage counts of American eels supported an additive-effects model (YR + LI + RDM) where parameter estimates were positive for river discharge (β = 7.3, s.e. = 0.01) and negative for LI (β = −1.9, s.e. = 0.34). Interestingly, RDM and LI acted synergistically and singularly as correlates of upstream migration of American eels, but the highest daily counts and multiple-day passage events were associated with increased RDM. Annual installation of the eel pass during late spring or summer prevented an early spring assessment, a period with higher RDM relative to those values obtained during sampling periods. Because increases in river discharge are climatically controlled events, upstream migration events of American eels within the Potomac River drainage are likely linked to the influence of climate variability on flow regime.

Riverdamming provides a dominant human impact on river environments worldwide, and while local impacts of reservoir flooding are immediate, subsequent ecological impacts downstream can be extensive. In this article, we assess seven research strategies for analyzing the impacts of dams and river flow regulation on riparian ecosystems. These include spatial comparisons of (1) upstream versus downstream reaches, (2) progressive downstream patterns, or (3) the dammedriver versus an adjacent free-flowing or differently regulated river(s). Temporal comparisons consider (4) pre- versus post-dam, or (5) sequential post-dam conditions. However, spatial comparisons are complicated by the fact that dams are not randomly located, and temporal comparisons are commonly limited by sparse historic information. As a result, comparative approaches are often correlative and vulnerable to confounding factors. To complement these analyses, (6) flow or sediment modifications can be implemented to test causal associations. Finally, (7) process-based modeling represents a predictive approach incorporating hydrogeomorphic processes and their biological consequences. In a case study of Hells Canyon, the upstream versus downstream comparison is confounded by a dramatic geomorphic transition. Comparison of the multiple reaches below the dams should be useful, and the comparison of Snake River with the adjacent free-flowing Salmon River may provide the strongest spatial comparison. A pre- versus post-dam comparison would provide the most direct study approach, but pre-dam information is limited to historic reports and archival photographs. We conclude that multiple study approaches are essential to provide confident interpretations of ecological impacts downstream from dams, and propose a comprehensive study for Hells Canyon that integrates multiple research strategies. PMID:18043964

Riverdamming provides a dominant human impact on river environments worldwide, and while local impacts of reservoir flooding are immediate, subsequent ecological impacts downstream can be extensive. In this article, we assess seven research strategies for analyzing the impacts of dams and river flow regulation on riparian ecosystems. These include spatial comparisons of (1) upstream versus downstream reaches, (2) progressive downstream patterns, or (3) the dammedriver versus an adjacent free-flowing or differently regulated river(s). Temporal comparisons consider (4) pre- versus post-dam, or (5) sequential post-dam conditions. However, spatial comparisons are complicated by the fact that dams are not randomly located, and temporal comparisons are commonly limited by sparse historic information. As a result, comparative approaches are often correlative and vulnerable to confounding factors. To complement these analyses, (6) flow or sediment modifications can be implemented to test causal associations. Finally, (7) process-based modeling represents a predictive approach incorporating hydrogeomorphic processes and their biological consequences. In a case study of Hells Canyon, the upstream versus downstream comparison is confounded by a dramatic geomorphic transition. Comparison of the multiple reaches below the dams should be useful, and the comparison of Snake River with the adjacent free-flowing Salmon River may provide the strongest spatial comparison. A pre- versus post-dam comparison would provide the most direct study approach, but pre-dam information is limited to historic reports and archival photographs. We conclude that multiple study approaches are essential to provide confident interpretations of ecological impacts downstream from dams, and propose a comprehensive study for Hells Canyon that integrates multiple research strategies.

Riverdamming provides a dominant human impact on river environments worldwide, and while local impacts of reservoir flooding are immediate, subsequent ecological impacts downstream can be extensive. In this article, we assess seven research strategies for analyzing the impacts of dams and river flow regulation on riparian ecosystems. These include spatial comparisons of (1) upstream versus downstream reaches, (2) progressive downstream patterns, or (3) the dammedriver versus an adjacent free-flowing or differently regulated river(s). Temporal comparisons consider (4) pre- versus post-dam, or (5) sequential post-dam conditions. However, spatial comparisons are complicated by the fact that dams are not randomly located, and temporal comparisons are commonly limited by sparse historic information. As a result, comparative approaches are often correlative and vulnerable to confounding factors. To complement these analyses, (6) flow or sediment modifications can be implemented to test causal associations. Finally, (7) process-based modeling represents a predictive approach incorporating hydrogeomorphic processes and their biological consequences. In a case study of Hells Canyon, the upstream versus downstream comparison is confounded by a dramatic geomorphic transition. Comparison of the multiple reaches below the dams should be useful, and the comparison of Snake River with the adjacent free-flowing Salmon River may provide the strongest spatial comparison. A pre- versus post-dam comparison would provide the most direct study approach, but pre-dam information is limited to historic reports and archival photographs. We conclude that multiple study approaches are essential to provide confident interpretations of ecological impacts downstream from dams, and propose a comprehensive study for Hells Canyon that integrates multiple research strategies. PMID:18043964

This study examines the effects of a large dam on hydrological droughts in the transboundary Tagus River, central Spain and Portugal. The magnitude and duration of droughts are analyzed by comparing a monthly drought index calculated for the flow series upstream and downstream of the Alcántara reservoir. The dam was built in 1969, and the reservoir is the second largest in Europe (3,162 hm3). Water management in the area is complex because of large seasonal and interannual variability in the flow regime, which is characteristic of Mediterranean environments. This paper demonstrates that, as a result of exploitation of the Alcántara reservoir, (1) during periods of water scarcity, the releases in winter and spring are reduced dramatically and the magnitude and duration of summer low flow show a slight increase and (2) the nature of droughts along the Tagus river basin downstream of the dam has shown severe changes since construction of the dam. In fact, during the predam period (1943-1969), droughts were longer and more intense in the Spanish part of the basin than that in the Portuguese part. Since the construction of the Alcántara dam, however, the Portuguese part of the basin has experienced more severe droughts than did the upstream part in terms of both magnitude and duration.

The geomorphic evolution of large European fluvial systems since the end of the nineteenth century has been determined, according to recent studies, by changes that have affected the drainage basins, notably climatic changes at the end of the Little Ice Age (LIA), agricultural practices, and successive phases of channel management involving embankments and dams. However, the respective roles of these various control factors in modifying sediment storage and channel stability are often difficult to identify. The aim of this paper is to determine the main factors that have driven morphological changes over the past 130 years on the 120-km-long downstream reach of the Rhône River. A GIS-based analysis of maps and aerial photographs available since 1860, coupled with chrono-stratigraphic data on the river's alluvial deposits, has enabled quantification of sediment storage and erosion in different morphological units. Changes measured include riverbed incision, narrowing of the main channel in relation with accumulation of fine sediments along the channel margins, and reduction of sediment input at the mouth. On the basis of local- and reach-scale sediment balances, we show that these changes are synchronous with engineering works carried out at the end of the nineteenth century and beginning of the twentieth century, a period that coincided with a decline in river sediment inputs largely generated by human activities. The early stabilisation of mountain slopes resulting from a decline in rural agriculture, rural exodus, reforestation and engineered torrent control has had a much greater impact in geomorphically transforming the Rhône than dams and gravel mining, the major identified causes of river destabilisation in the world. This calls for caution in the all-too-common and wholesale attribution of declining sediment budgets of European rivers, especially in the Mediterranean region, to dams.

We investigated upstream reservoir sediment erosion and channel evolution of the Blackfoot River, MT, following the 2008 removal of Milltown Dam, which is located on the Clark Fork River at its confluence with the Blackfoot River. The removal of Milltown Dam has garnered substantial attention because of the presence of contaminated sediments in the Clark Fork arm of Milltown Reservoir, but river erosion of uncontaminated sediments from the Blackfoot arm of Milltown reservoir has provided an opportunity to examine river response to base-level lowering. We tracked reservoir sediment evacuation by surveying water surface profiles at multiple stages and bed topography before and after dam breaching. These data, in combination with HEC- RAS modeling, are being used to examine the spatial and temporal patterns of reservoir erosion. The 9 m base level reduction resulting from the dam removal, combined with snowmelt runoff with a peak flow recurrence interval of approximately 4 years in spring and summer 2008, produced erosion and downstream transport of >100 years of accumulated sediment in the first several months following dam breaching. Response to the base level reduction travelled approximately 750 m past the upper extent of the historical reservoir (approximately 3.75 km from Milltown dam). Net degradation in the upper 500 m of the reservoir, and net aggradation downstream of a confined flume-like reach (through which eroded sediment was passed) was found. In the lower 1.5 km of the historic reservoir, the river scoured up to 3 m-thick silt and sand deposits, and a complex, multiple-channel configuration developed. This lower reservoir reach is now characterized by alternating point and mid-channel bars surrounded by log jams that organized from cut timber mobilized from channel margins and exhumed from the bed during incision. We observed channel incision and subsequent widening into the coarse, unconsolidated deltaic deposit in the upper reservoir which eroded

Electromyogram (EMG) radiotelemetry was used to examine the amount of energy expended by spring Chinook salmon Oncorhynchus tshawytscha migrating upstream past a Columbia Riverdam. Electrodes from EMG transmitters were surgically implanted in the red muscle of fish captured at Bonneville Dam and output from the tags was calibrated to defined swim speeds for each fish in a tunnel respirometer. The fish were then released below Bonneville Dam and radio-tracked as they migrated through the tailraces, fishways, and forebays of the dam. On average, the rate of aerobic energy used by spring Chinook salmon was significantly higher when they were moving through tailraces (1.27 kcal•kg-1•h-1) than when they were moving through other parts of the dam. Specifically, the rate of aerobic energy use for fish in tailraces was 14% higher than that used by fish in fishways (1.11 kcal•kg-1•h-1) and 27% higher than the rate used by fish in forebays (1.00 kcal•kg-1•h-1). Most (80%) of the aerobic energy used by fish to pass this dam was expended in the tailrace (25.5 kcal/kg), while only 18% (5.6 kcal/kg) and 2% (0.6 kcal/kg) were used in the fishways and forebays.

Electromyogram (EMG) radiotelemetry was used to estimate the swim speeds of spring Chinook salmon Oncorhynchus tshawytscha migrating upstream past a Columbia Riverdam. Electrodes from EMG transmitters were surgically implanted in the red muscle of fish captured at Bonneville Dam, and output from the tags was calibrated to defined swim speeds for each fish in a tunnel respirometer. The fish were then released below Bonneville Dam and radio-tracked as they migrated through the tailraces, fishways, and forebays of the dam. On average, swim speed was significantly higher when tagged salmon were moving through tailraces than when they were moving through other parts of the dam. Specifically, swim speeds for fish in tailraces (106.4 cm/s) were 23% higher than those of fish in fishways (84.9 cm/s) and 32% higher than those of fish in forebays (80.2 cm/s). Swim speeds were higher in fishways during the day than during the night, but there were no diel differences in swim speeds in tailraces and forebays. During dam passage, Chinook salmon spent the most time in tailraces, followed by fishways and forebays. ?? Copyright by the American Fisheries Society 2006.

Much has been written on the hydrology of the Yangtze River in China, especially since the construction of the Three Gorges Dam. Given the range of views in the literature on the impacts of dams and other natural and anthropogenic activities in the catchment on monthly flows, we here set out to analyse the behavior of monthly flows over the period of record 1955-2014. In the literature, the Three Gorges dam has been singled out for particular comment, mostly adverse. In this paper we analyse trend in temperature, precipitation and discharge of the Yangtze River at the monthly time scale over a period that includes the 11 years since the Three Gorges Dam came into operation. The results show that for the upper basin, there has been a marked increase in discharge in the low flow months of January to March that began abruptly in 2003 and an abrupt decrease in flow in October at the same time. Similar changes are found for discharge from the lower basin but in that case the changes have occurred gradually over the period of record. These changes are the outcome of the operation of hydroelectric and flood control dams that have been built continuously in the lower basin since 1955 while in the upper basin the building of the Three Gorges Dam began a phase of rapid dam building not seen in the lower basin. The decreased flows in the late summer and autumn are not of sufficient magnitude to cause any problems for navigation or water supply. The enhanced flows in the winter low flow period are beneficial in that they reduce the likelihood of salt water intrusions in the estuary adversely affecting the supply of freshwater to Shanghai.

This report contains water-quality data for the Ohio River, collected during the summer and fall of 1992, from river mile 51.1 (3.3 miles upstream from New Cumberland Dam) to river mile 84.0 (0.2 miles upstream from Pike Island Dam). The data were collected to assess the effects of hydropower development on water quality. Water quality was determined by a combination of repeated synoptic field measurements and laboratory analyses. Synoptic measurements were made along a longitudinal transect with 18 mid-channel sampling sites; cross-sectional transects of water quality were measured at 5 of these sites. Water-quality measurements also were made at two sites located on the back-channel (Ohio) side of Browns Island. Water temperature, dissolved oxygen concentration, pH, and specific conductance were measured at each longitudinal-transect and back-channel sampling site. Longitudinal-transect and back-channel stations were sampled at three depths (about 3.3 feet below the surface of the water, middle of the water column, and near the bottom of the river). Cross-sectional transects consisted of three or four detailed vertical pro- files of the same characteristics. Water samples were collected from three depths at the mid-channel vertical profile in each cross-sectional transect and were analyzed for concentrations of phyto- plankton photosynthetic pigments chlorophyll a and chlorophyll b. Estimates of the depth of light penetration (Secchi disk transparency) were made at pigment-sampling locations whenever light and river-surface conditions were appropriate. Synoptic sampling usually was completed in 12 hours or less and was repeated seven times between June 25 and November 6, 1992.

In the recent past the concept of connectivity gained increased significance for the understanding of the linkage between different subsystems within river channels and catchments. Based on fine sediment (<2mm) analyses the main objective of the presented work is to analyse the impact of a dam on the longitudinal sediment connectivity in a river channel. The study sites are located alongside the "Kaja" river (lower Austria), which has a catchment area of about 21.3km2. The river is characterised by a series of dams whereof the present work deals with the so called "Sagteich". Measurements of suspended load as well as fine sediment samples from pool-sections were collected up- and downstream of the dam. The suspended load concentrations where analysed by weighting the water and sediment amount. The grain size distribution of the sediment samples from the pool-sections were measured with sieving as well as pipette analyses. The results of the suspended load analysis reveal that the dam is a strong disconnecting factor in longitudinal direction. This disconnectivity cannot be confirmed for fine sediments, which have been determined from the sediment samples collected in the pool-sections. It is argued, that the lateral input of sediments alters the grain size distribution in pool-sections and consequently, any interpretation of longitudinal sediment connectivity, or disconnectivity has to be regarded with reservation in this fraction.

A pilot study was conducted to estimate survival of hatchery-reared yearling chinook salmon through dams and reservoirs on the Snake River. The goals of the study were to: (1) field test and evaluate the Single-Release, Modified-Single-Release, and Paired-Release Models for the estimation of survival probabilities through sections of a river and hydroelectric projects; (2) identify operational and logistical constraints to the execution of these models; and (3) determine the usefulness of the models in providing estimates of survival probabilities. Field testing indicated that the numbers of hatchery-reared yearling chinook salmon needed for accurate survival estimates could be collected at different areas with available gear and methods. For the primary evaluation, seven replicates of 830 to 1,442 hatchery-reared yearling chinook salmon were purse-seined from Lower Granite Reservoir, PIT tagged, and released near Nisqually John boat landing (River Kilometer 726). Secondary releases of PIT-tagged smolts were made at Lower Granite Dam to estimate survival of fish passing through turbines and after detection in the bypass system. Similar secondary releases were made at Little Goose Dam, but with additional releases through the spillway. Based on the success of the 1993 pilot study, the authors believe that the Single-Release and Paired-Release Models will provide accurate estimates of juvenile salmonid passage survival for individual river sections, reservoirs, and hydroelectric projects in the Columbia and Snake Rivers.

In 1996, the National Marine Fisheries Service and the University of Washington completed the fourth year of a multi-year study to estimate survival of juvenile salmonids (Oncorhynchus spp.) passing through dams and reservoirs on the Snake River. Actively migrating smolts were collected near the head of Lower Granite Reservoir and at Lower Granite Dam, tagged with passive integrated transponder (PIT) tags, and released to continue their downstream migration. Individual smolts were subsequently detected at PIT-tag detection facilities at Lower Granite, Little Goose, Lower Monumental, McNary, John Day and Bonneville Dams. Survival estimates were calculated using the Single-Release (SR) and Paired-Release (PR) Models. Timing of releases of tagged hatchery steelhead (O. mykiss) from the head of Lower Granite Reservoir and yearling chinook salmon (O. tshawytscha) from Lower Granite Dam in 1996 spanned the major portion of their juvenile migrations. Specific research objectives in 1996 were to (1) estimate reach and project survival in the Snake River using the Single-Release and Paired-Release Models throughout the yearling chinook salmon and steelhead migrations, (2) evaluate the performance of the survival-estimation models under prevailing operational and environmental conditions in the Snake River, and (3) synthesize results from the 4 years of the study to investigate relationships between survival probabilities, travel times, and environmental factors such as flow levels and water temperature.

Amounts of radionuclides from the Hanford reactors contained in bed sediments of the Columbia River were estimated by two methods: (1) from data on radionuclide concentration for the bed sediments between the reactors and McNary Dam, and (2) from data on radionuclide discharge for river stations at Pasco, Washington, and Umatilla, Oregon. Umatilla is 3.2 kilometers below McNary Dam. Accumulations of radionuclides in the Pasco to Umatilla reach estimated by the two methods agree within about 8%. In October 1965 approximately 16,000 curies of gamma emitting radionuclides were resident in bed sediments of the river between the Hanford reactors and McNary Dam. Concentrations and accumulations of chromium-51, zinc-65, cobalt-60, manganese-54, and scandium-46 generally are much higher near McNary Dam than they are in the vicinity of the reactors. These changes are caused by an increase downstream from the reactors in the proportion of the bed sediment that is fine grained and the proportions of the transported zinc, cobalt, manganese, and scandium radionuclides associated with sediment particles.

In 1994, the National Marine Fisheries Service and the University of Washington completed the second year of a multi-year study to estimate survival of juvenile salmonids (Oncorhynchus spp.) passing through the dams and reservoirs of the Snake River. Actively migrating smolts were collected at selected locations above, at, and below Lower Granite Dam, tagged with passive integrated transponder (PIT) tags, and released to continue their downstream migration. Survival estimates were calculated using the Single-Release, Modified Single-Release, and Paired-Release Models.

As the largest hydropower project in the world, the Three Gorges Dam (TGD) has attracted great concerns in terms of its impact on the Changjiang (Yangtze) River and coastal marine environments. In this study, we measured or collected the H-O isotopic data of river water, groundwater and precipitation in the mid-lower Changjiang catchment during the dry seasons of recent years. The aim was to investigate the changes of river water cycle in response to the impoundment of the TGD. Isotopic evidences suggested that the mid-lower Changjiang river water was ultimately derived from precipitation, but dominated by the mixing of different water masses with variable sources and isotopic signals as well. The isotopic parameter "deuterium excess" (d-excess) yielded large fluctuations along the mid-lower mainstream during the initial stage of the TGD impoundment, which was inherited from the upstream water with inhomogeneous isotopic signals. However, as the reservoir water level rising to the present stage, small variability of d-excess was observed along the mid-lower mainstream. This discrepancy could be explained that the TGD impoundment had significantly altered the water cycle downstream the dam, with the rising water level increasing the residence time and enhancing the mixing of reservoir water derived from upstream. This eventually resulted in the homogenization of reservoir water, and thus small fluctuations of d-excess downstream the dam after the quasi-normal stage (2008 to present). We infer that the retention effect of large reservoirs has greatly buffered the d-excess natural variability of water cycle in large river systems. Nevertheless, more research attention has to be paid to the damming effect on the water cycle in the river, estuarine and coastal areas, especially during the dry seasons. PMID:27096630

River reaches upstream from dam reservoirs, where water level fluctuations occur due to backwater effects, may be utilized as a field laboratory of base-level rise effects on river morphology. Here I present the results of the aerial photo-based (1963-2012) reconstruction of the long-term morphological adjustments of the small, gravel-bed Smolnik River in the backwater of the Rożnów Reservoir (1941) (Southern Poland). Channel narrowing and the formation of a relatively stable single-thread, high sinuosity channel with densely vegetated banks were observed in this zone due to forced fine and coarse sediments deposition connected with the backwater effects of the reservoir. This study has shown that specific river morphology may relatively quickly develop in the backwater zones of dam reservoirs as an effect of disturbances in the sediment and water transport connected with the base-level rise. This study also suggests that long-term river morphological adjustments in the backwater seem to be significantly controlled by the dynamic feedback between the fine sediments deposition and vegetation expansion that facilitate the development and maintenance of a single-thread, high sinuosity channel.

In 1991 and 1992, the National Marine Fisheries Service completed the second and third years of a 3-year study to estimate juvenile salmonid (Oncorhynchus spp.) timing and survival characteristics related to passage through the Prosser Dam complex, including the Chandler Canal and the Chandler fish collection facility, on the Yakima River. Yearling chinook (O. tshawyacha) and coho salmon (O. kisutch) were collected at the Chandler facility, PIT tagged, and released at various locations in the Yakima River, Chandler Canal, and the Chandler facility. Individual fish were subsequently detected at PIT-tag detection monitors at the Chandler facility and/or McNary Dam on the Columbia River. Survival through various reaches, PIT-tag detection efficiency, and Chandler Canal fish entrainment proportion parameters were estimated using maximum likelihood techniques. The research objectives in 1991 and 1992 were to: (1) assess the effects of passage through the Chandler Canal and the Chandler facility on the survival of juvenile salmonids, (2) determine the entrainment rate of juvenile salmonids into the Chandler Canal as a function of river flow, and (3) determine the efficiency and reliability of the PIT-tag monitoring system at the Chandler facility. The initial 1990 research plan was expanded in 1991 and 1992 to include several more release locations and many more release days.

The southwestern willow flycatcher ( Empidonax traillii extimus) is a riparian bird that spends winter months in Central and South America and summer breeding months in riparian zones of the American Southwest. Decline of the willow flycatcher population to less than 1000 breeding pairs prompted the Federal government to declare the species endangered, triggering a major recovery effort. The most important aspect of recovery is management and improvement of the riparian habitat of the bird population. Although the direct management of the species is primarily a biological issue, fluvial hydrology and geomorphology play an important role in understanding the dynamics of the present bird population and in designing a recovery plan because these physical systems are the substrates for the living communities which include the birds. Contributions of geomorphology and hydrology to the recovery plan include the use of watersheds and river basins as planning and evaluation units; understanding the connections between fluvial forms and riparian vegetation; implications for the bird population of the magnitude, frequency, duration, timing, and rate of change for various river discharges. The installation and operation of dams are the most important causes of hydro-geomorphic and ecological change in the region, so that management of these structures offers primary opportunities to improve the physical and biological conditions for the endangered species.

Reservoirs on rivers can disrupt organic carbon (OC) transport and transformation, but less is known how river reaches directly below dams contribute to OC processing. We compared how reservoirs and their associated tailwaters affected OC quantity and quality by calculating particulate OC (POC) and dissolved OC (DOC) fluxes, and measuring composition and bioavailability of DOC. We sampled the Yampa River near Maybell, Colorado, USA, and the Green River above and below Fontenelle and Flaming Gorge reservoirs as well as their respective tailwaters from early snowmelt to base flow hydrological conditions. In unregulated reaches (Yampa River, Green River above Fontenelle reservoir), DOC and POC concentrations increased with snowmelt discharge. POC and DOC concentrations also increased with stream discharge below Fontenelle reservoir, but there was no relationship between DOC and stream flow below Flaming Gorge reservoir. The annual load of POC was 3-fold lower below Fontenelle Reservoir and nearly 7-fold lower below Flaming Gorge reservoir, compared to their respective upstream sampling sites. DOC exported to downstream reaches from both reservoirs was less bioavailable, as measured with bioassays, than DOC upriver of the reservoirs. Lastly, tailwater reaches below the reservoirs generated OC, exporting potentially 1.6-2.2 g C m-2 d-1 of OC to downstream ecosystems. Therefore, the effect of impounding rivers on C fluxes is greater than the impact of the reservoirs alone given the additive effect of tailwater reaches below dams, which may produce and export comparable amounts of likely autochthonous carbon to downstream reaches.

In unimpounded rivers, Pacific salmon (Oncorhynchus spp.) typically spawn under relatively stable stream flows, with exceptions occurring during periodic precipitation events. In contrast, hydroelectric development has often resulted in an artificial hydrograph characterized by rapid changes in discharge and tailwater elevation that occur on a daily, or even an hourly basis, due to power generation (Cushman 1985; Moog 1993). Consequently, populations of Pacific salmon that are known to spawn in main-stem habitats below hydroelectric dams face the risks of changing habitat suitability, potential redd dewatering, and uncertain spawning success (Hamilton and Buell 1976; Chapman et al. 1986; Dauble et al. 1999; Garland et al. 2003; Connor and Pflug 2004; McMichael et al. 2005). Although the direct effects of a variable hydrograph, such as redd dewatering are apparent, specific effects on spawning behavior remain largely unexplored. Chum salmon (O. keta) that spawn below Bonneville Dam on the Columbia River are particularly vulnerable to the effects of water level fluctuations. Although chum salmon generally spawn in smaller tributaries (Johnson et al. 1997), many fish spawn in main-stem habitats below Bonneville Dam near Ives Island (Tomaro et al. 2007; Figure 1). The primary spawning area near Ives Island is shallow and sensitive to changes in water level caused by hydroelectric power generation at Bonneville Dam. In the past, fluctuating water levels have dewatered redds and changed the amount of available spawning habitat (Garland et al. 2003). To minimize these effects, fishery managers attempt to maintain a stable tailwater elevation at Bonneville Dam of 3.5 m (above mean sea level) during spawning, which ensures adequate water is provided to the primary chum salmon spawning area below the mouth of Hamilton Creek (Figure 1). Given the uncertainty of winter precipitation and water supply, this strategy has been effective at restricting spawning to a specific

The tracing of Rhodamine WT dye has provided time-of-travel data for waste-load allocation studies of a 42.8-mile reach of the Flint River at low flow. Dye was injected at two locations in Flint--at Utah Dam and at Grand Traverse Street. From Utah Dam to Grand Traverse Street the mean velocity of flow was 0.1 foot per second; time-of-travel was 35.3 hours. From Grand Traverse Street to Highway M-13, mean velocity was 0.7 foot per second; time-of-travel was 78.8 hours. Time-of-travel for the reach between Utah Dam and Highway M-13 was thus 114 hours. A discharge of equaled or exceeded about 90% of the time was measured at Grand Traverse Street in Flint before dye injection. (USGS)

Ephemeral dams caused by landslides have been observed around the world, yet little is known about the effects of their failure on landforms and vegetation. In 1967, a landslide-dam-break flood in a pristine reach of the Elwha River valley filled the former channel and diverted the river. The reach is a reference site for restoration following the planned removal of dams on the river. We identified five surfaces on the 25 ha debris fan deposited by the flood. Based on tree ages and historic air photos, three of the surfaces formed in 1967, while two formed later. The surfaces varied in substrate (silt and sand, to boulders), and height above the river channel. Tree mortality resulted from tree removal and burial by sediment, the latter leaving snags and some surviving trees. Tree species composition was generally consistent within each surface. Dominant species included red alder (Alnus rubra) and Sitka willow (Salix sitchensis), alone or in combination, a combination of Douglas-fir (Pseudotsuga menziesii) and black cottonwood (Populus balsamifera ssp. trichocarpa), or a combination of alder and Cottonwood. There were significant differences between surfaces in stem density, basal area, and rate of basal area growth. The large degree of heterogeneity in forest structure, composition, and productivity within a relatively small floodplain feature is in part due to spatial variability in the intensity of a single disturbance event, and in part due to the occurrence of subsequent, smaller events. To recreate natural diversity of riparian forests may require mimicking the variety of physical and biotic habitats that a single, complex disturbance event may create.

From 1987 to 1992, we evaluated a fish bypass system at Bonneville Dam Powerhouse 2 on the Columbia River. The survival of subyearling Chinook salmon Oncorhynchus tshawytscha released into the system ranged from 0.774 to 0.911 and was significantly lower than the survival of test fish released into turbines and the area immediately below the powerhouse where bypass system flow reentered the river. Yearling and subyearling Chinook salmon and yearling coho salmon O. kisutch released into the bypass system were injured or descaled. Also, levels of blood plasma cortisol and lactate were significantly higher in yearling and subyearling Chinook salmon that passed through the bypass system than in fish released directly into a net located over the bypass exit. This original system was then extensively modified using updated design criteria, and the site where juvenile fish reentered the river was relocated 2.8 km further downstream to reduce predation on bypassed fish by northern pikeminnow Ptychocheilus oregonensis. Based on studies conducted from 1999 to 2001, the new bypass system resulted in high fish survival, virtually no injuries to fish, fish passage times that were generally similar to water travel times, and mild stress responses from which fish recovered quickly. The mean estimated survival of subyearling Chinook salmon passing through the new bypass system was 0.946 in 2001, which was an usually low-flow year. Survival, physical condition, passage timing, and blood physiological indicators of stress were all useful metrics for assessing the performance of both bypass systems and are discussed. The engineering and hydraulic criteria used to design the new bypass system that resulted in improved fish passage conditions are described.

The Link River to Keno Dam (Link-Keno) reach of the Klamath River, Oregon, generally has periods of water-quality impairment during summer, including low dissolved oxygen, elevated concentrations of ammonia and algae, and high pH. Efforts are underway to improve water quality in this reach through a Total Maximum Daily Load (TMDL) program and other management and operational actions. To assist in planning, a hydrodynamic and water-quality model was used in this study to provide insight about how various actions could affect water quality in the reach. These model scenarios used a previously developed and calibrated CE-QUAL-W2 model of the Link-Keno reach developed by the U.S. Geological Survey (USGS), Watercourse Engineering Inc., and the Bureau of Reclamation for calendar years 2006-09 (referred to as the "USGS model" in this report). Another model of the same river reach was previously developed by Tetra Tech, Inc. and the Oregon Department of Environmental Quality for years 2000 and 2002 and was used in the TMDL process; that model is referred to as the "TMDL model" in this report. This report includes scenarios that (1) assess the effect of TMDL allocations on water quality, (2) provide insight on certain aspects of the TMDL model, (3) assess various methods to improve water quality in this reach, and (4) examine possible water-quality effects of a future warmer climate. Results presented in this report for the first 5 scenarios supersede or augment those that were previously published (scenarios 1 and 2 in Sullivan and others [2011], 3 through 5 in Sullivan and others [2012]); those previous results are still valid, but the results for those scenarios in this report are more current.

To date, a number of reports have been published on the relation of cigarette smoking to age-related maculopathy, an important cause of blindness in the United States. However, few studies have examined the relation between smoking and the incidence of age-related maculopathy. In this report, the authors examine this association in persons aged 43-86 years (n = 3,583) at baseline who were participants in the baseline examination and 5-year follow-up of the Beaver Dam Eye Study, Beaver Dam, Wisconsin (1988-1990 and 1993-1995). Exposure data on cigarette smoking were obtained from questions about present and past smoking, duration of smoking, and the number of cigarettes smoked per day. Age-related maculopathy status was determined by grading stereoscopic color fundus photographs using the Wisconsin Age-related Maculopathy Grading System. After controlling for age, sex, vitamin supplement use, and beer consumption, men who smoked greater amounts of cigarettes were more likely to develop early age-related maculopathy (odds ratio (OR) per 10 pack-years smoked = 1.06, 95% confidence interval (CI) 1.00-1.13, p = 0.06) than men who had smoked less. This association was not observed in women. Men (OR = 3.21, 95% CI 1.09-9.45) and women (OR = 2.20, 95% CI 1.04-4.66) who were current smokers at the time of the baseline examination had significantly higher odds of developing large drusen (> or = 250 microns in diameter) after 5 years than those who had never smoked or who quit before the baseline study. Current or past history of cigarette smoking was not related to the incidence of retinal pigment epithelial depigmentation. The authors conclude that smoking appears to be related to the incidence of some lesions associated with early age-related maculopathy. PMID:9456998

The global number of dam constructions has increased dramatically over the past six decades and is forecast to continue to rise, particularly in less industrialized regions. Identifying development pathways that can deliver the benefits of new infrastructure while also maintaining healthy and productive river systems is a great challenge that requires understanding the multifaceted impacts of dams at a range of scales. New approaches and advanced methodologies are needed to improve predictions of how future dam construction will affect biodiversity, ecosystem functioning, and fluvial geomorphology worldwide, helping to frame a global strategy to achieve sustainable dam development. Here, we respond to this need by applying a graph-based river routing model to simultaneously assess flow regulation and fragmentation by dams at multiple scales using data at high spatial resolution. We calculated the cumulative impact of a set of 6374 large existing dams and 3377 planned or proposed dams on river connectivity and river flow at basin and subbasin scales by fusing two novel indicators to create a holistic dam impact matrix for the period 1930-2030. Static network descriptors such as basin area or channel length are of limited use in hierarchically nested and dynamic river systems, so we developed the river fragmentation index and the river regulation index, which are based on river volume. These indicators are less sensitive to the effects of network configuration, offering increased comparability among studies with disparate hydrographies as well as across scales. Our results indicate that, on a global basis, 48% of river volume is moderately to severely impacted by either flow regulation, fragmentation, or both. Assuming completion of all dams planned and under construction in our future scenario, this number would nearly double to 93%, largely due to major dam construction in the Amazon Basin. We provide evidence for the importance of considering small to medium sized

The Hoa Binh dam (HBD), located on a tributary of the Red River in Vietnam, has a capacity of 9.45 × 109 m3 and was commissioned in December 1988. Although it is important for flood prevention, electricity production and irrigation in northern Vietnam, the Hoa Binh dam has also highly influenced the suspended sediment distribution in the lower Red River basin, in the delta and in the coastal zone. Its impact was analysed from a 50-year data set of water discharge and suspended sediment concentration (1960-2010), and the distribution of water and sediment across the nine mouths of the delta was simulated using the MIKE11 numerical model before and after the dam settlement. Although water discharge at the delta inlet decreased by only 9%, the yearly suspended sediment flux dropped, on average, by 61% at Son Tay near Hanoi (from 119 to 46 × 106 t yr-1). Along the coast, reduced sedimentation rates are coincident with the lower sediment delivery observed since the impoundment of the Hoa Binh dam. Water regulation has led to decreased water discharge in the wet season (-14% in the Red River at Son Tay) and increased water discharge in the dry season (+12% at the same station). The ratios of water and suspended sediment flows, as compared to the total flows in the nine mouths, increased in the northern and southern estuaries and decreased in the central, main Ba Lat mouth. The increasing volume of dredged sediments in the Haiphong harbour is evidence of the silting up of the northern estuary of Cam-Bach Dang. The effect of tidal pumping on enhanced flow occurring in the dry season and resulting from changed water regulation is discussed as a possible cause of the enhanced siltation of the estuary after Hoa Binh dam impoundment.

This assessment addresses the impacts to the wildlife populations and wildlife habitats due to the Libby Dam project on the Kootenai River and previous mitigation of these losses. The current assessment documents the best available information concerning the impacts to the wildlife populations inhabiting the project area prior to construction of the dam and creation of the reservoir. Many of the impacts reported in this assessment differ from those contained in the earlier document compiled by the Fish and Wildlife Service; however, this document is a thorough compilation of the available data (habitat and wildlife) and, though conservative, attempts to realistically assess the impacts related to the Libby Dam project. Where appropriate the impacts resulting from highway construction and railroad relocation were included in the assessment. This was consistent with the previous assessments.

Efforts have been initiated to develop a research plan that will provide insight into causes of, and ultimately solutions to, the apparent excessive mortality of juvenile chinook upstream from Lower Granite Dam on the Snake River. In the context of the proposed salmon stock listings under the Endangered Species Act, issues that potentially affect wild stocks of spring chinook salmon probably warrant immediate consideration and resolution. Mark-recapture data at Lower Granite Dam indicate that few yearling chinook salmon (Oncorhynchus tshawytscha) smolts survive to that site after release from various hatcheries. Upriver stocks of yearling spring and summer chinook exhibit pronounced losses en route to the dam. In 1989 and 1990, only about 8 to 18% of PIT-tagged representatives from McCall or Sawtooth hatchery were detected at the dam. General survival indices for these stocks indicate that perhaps only 15 to 35% of the yearlings survived to that site. This suggests these stocks may sustain as much mortality traversing this unobstructed reach of river as the general population would passing through the entire hydroelectric complex.

Dams impact the survival of juvenile anadromous fishes by obstructing migration corridors, lowering water quality, delaying migrations, and entraining fish in turbine discharge. To reduce these impacts, structural and operational modifications to dams— such as voluntary spill discharge, turbine intake guidance screens, and surface flow outlets—are instituted. Over the last six years, we have used acoustic imaging technology to evaluate the effects of these modifications on fish behavior, passage rates, entrainment zones, and fish/flow relationships at hydroelectric projects on the Columbia River. The imaging technique has evolved from studies documenting simple movement patterns to automated tracking of images to merging and analysis with concurrent hydraulic data. This chapter chronicles this evolution and shows how the information gleaned from the scientific evaluations has been applied to improve passage conditions for juvenile salmonids. We present data from Bonneville and The Dalles dams that document fish behavior and entrainment zones at sluiceway outlets (14 to 142 m3/s), fish passage rates through a gap at a turbine intake screen, and the relationship between fish swimming effort and hydraulic conditions. Dam operators and fisheries managers have applied these data to support decisions on operational and structural changes to the dams for the benefit of anadromous fish populations in the Columbia River basin.

The Mekong River delta plays an important role in the Vietnamese economy and it has been severely impacted during this century by a series of unusually large floods. In the dry season the delta is also impacted by salinity intrusion and tides. These effects have caused severe human hardship. To mitigate these impacts, a large number of engineering structures, primarily dykes and weirs, have been built in the delta in recent years and are still being built, mainly to control floods and saltwater intrusion. These control measures are still being upgraded. A GIS-linked numerical model shows that the flood levels in the delta depend on the combined impacts of high river flows in the Mekong River, storm surges, sea level rise, and the likely, future siltation of the Mekong Estuary resulting from the construction of dams in China as well as many other dams proposed throughout the remaining river catchment. The model suggests that the engineering structures in the delta increase the flow velocities in the rivers and canals, increasing bank erosion, and cause the water to be deeper in the rivers and canals. This increases flooding in the non-protected areas of the delta and increases the risk of catastrophic failure of the dykes in the protected areas. The model also predicts that a sea level rise induced by global warming will enhance flooding in the Mekong River delta in Vietnam, and that flooding may worsen in the long term as a result of estuarine siltation resulting from the construction of dams. At the scale of the Mekong River basin, a multinational water resources management plan is needed that includes the hydrological needs of the delta. At the scale of the delta, a compromise is needed between allowing some flooding necessary for agriculture and preventing catastrophic flooding to alleviate human suffering.

Since FY 2000, scientists at Pacific Northwest National Laboratory (PNNL) have conducted research to assess the extent of spawning by chum (Oncorhynchus keta) and fall Chinook (O. tshawytscha) salmon in the lower mainstem Columbia River. Their work supports a larger Bonneville Power Administration (BPA) project aimed at characterizing the physical habitat used by mainstem fall Chinook and chum salmon populations. Multiple collaborators in addition to PNNL are involved in the BPA project--counterparts include the Washington Department of Fish and Wildlife (WDFW), U.S. Fish and Wildlife Service (USFWS), Pacific States Marine Fisheries Commission (PSMFC), U.S. Geological Survey (USGS), and Oregon Department of Fish and Wildlife (ODFW). Data resulting from the individual tasks each agency conducts are providing a sound scientific basis for developing strategies to operate the Federal Columbia River Power System (FCRPS) in ways that will effectively protect and enhance the chum and fall Chinook salmon populations--both listed as threatened under the Endangered Species Act. Fall Chinook salmon, thought to originate from Bonneville Hatchery, were first noted to be spawning downstream of Bonneville Dam by biologists from the WDFW in 1993. Known spawning areas include gravel beds on the Washington side of the river near Hamilton Creek and Ives Island. Limited spawning ground surveys were conducted in the area around Ives and Pierce islands during 1994 through 1997. Based on these surveys, fall Chinook salmon were believed to be spawning successfully in this area. In addition, chum salmon have been documented spawning downstream of Bonneville Dam. In FY 1999, BPA Project No. 1999-003 was initiated by the WDFW, ODFW, and the USFWS to characterize the variables associated with physical habitat used by mainstem fall Chinook and chum salmon populations and to better understand the effects of hydropower project operations on spawning and incubation. Pacific Northwest National

This research was conducted in the middle Duratón River (Central Spain), in the vicinity of Burgomillodo Reservoir. An industrial effluent enters the river 300 m downstream from the dam. Fluoride and turbidity levels significantly increased downstream from the effluent, these levels being to some extent affected by differential water releases from the dam. The community of submersed macrophytes exhibited slighter responses and, accordingly, lower discriminatory power than the community of benthic macroinvertebrates, this indicating that metrics and indices based on macroinvertebrates may be more suitable for the biological monitoring of water pollution and habitat degradation in dammedrivers receiving industrial effluents. However, in relation to fluoride bioaccumulation at the organism level, macrophytes (Fontinalis antipyretica and Potamogeton pectinatus) were as suitable bioindicators of fluoride pollution as macroinvertebrates (Ancylus fluviatilis and Pacifastacus leniusculus). Fluoride bioaccumulation in both hard and soft tissues of these aquatic organisms could be used as suitable bioindicator of fluoride pollution (even lower than 1 mg F(-)L(-1)) in freshwater ecosystems. Echinogammarus calvus exhibited a great sensitivity to the toxicity of fluoride ions, with a 96 h LC₅₀ of 7.5 mg F(-)L(-1) and an estimated safe concentration of 0.56 mg F(-)L(-1). The great capacity of E. calvus to take up and retain fluoride during exposures to fluoride ions would be a major cause of its great sensitivity to fluoride toxicity. It is concluded that the observed fluoride pollution might be partly responsible for the absence of this native amphipod downstream from the industrial effluent. PMID:23830885

Current management of the Klamath River includes prescribed minimum discharges intended partly to increase survival of juvenile coho salmon during their seaward migration in the spring. To determine if fish survival was related to river discharge, we estimated apparent survival and migration rates of yearling coho salmon in the Klamath River downstream of Iron Gate Dam. The primary goals were to determine if discharge at Iron Gate Dam affected coho salmon survival and if results from hatchery fish could be used as a surrogate for the limited supply of wild fish. Fish from hatchery and wild origins that had been surgically implanted with radio transmitters were released into the Klamath River slightly downstream of Iron Gate Dam at river kilometer 309. Tagged fish were used to estimate apparent survival between, and passage rates at, a series of detection sites as far downstream as river kilometer 33. Conclusions were based primarily on data from hatchery fish, because wild fish were only available in 2 of the 4 years of study. Based on an information-theoretic approach, apparent survival of hatchery and wild fish was similar, despite differences in passage rates and timing, and was lowest in the 54 kilometer (km) reach between release and the Scott River. Models representing the hypothesis that a short-term tagging- or handling-related mortality occurred following release were moderately supported by data from wild fish and weakly supported by data from hatchery fish. Estimates of apparent survival of hatchery fish through the 276 km study area ranged from 0.412 (standard error [SE] 0.048) to 0.648 (SE 0.070), depending on the year, and represented an average of 0.790 per 100 km traveled. Estimates of apparent survival of wild fish through the study area were 0.645 (SE 0.058) in 2006 and 0.630 (SE 0.059) in 2009 and were nearly identical to the results from hatchery fish released on the same dates. The data and models examined supported positive effects of water

... regulations of the Secretary of War relating to the use of the Mississippi River for the generation of power... Secretary of War, March 26, 1908, are rescinded, and the following regulations will govern the operation of... approximately 64,000 cubic feet per second, which corresponds to a normal stage of 6 feet above low water...

... regulations of the Secretary of War relating to the use of the Mississippi River for the generation of power... Secretary of War, March 26, 1908, are rescinded, and the following regulations will govern the operation of... approximately 64,000 cubic feet per second, which corresponds to a normal stage of 6 feet above low water...

... regulations of the Secretary of War relating to the use of the Mississippi River for the generation of power... Secretary of War, March 26, 1908, are rescinded, and the following regulations will govern the operation of... approximately 64,000 cubic feet per second, which corresponds to a normal stage of 6 feet above low water...

... regulations of the Secretary of War relating to the use of the Mississippi River for the generation of power... Secretary of War, March 26, 1908, are rescinded, and the following regulations will govern the operation of... approximately 64,000 cubic feet per second, which corresponds to a normal stage of 6 feet above low water...

We report on our progress from April 1989 through March 1990 on determining the status and habitat requirements of white sturgeon populations in the Columbia River downstream from McNary Dam. The study is a cooperative effort by the Oregon Department of Fish and Wildlife (ODFW), Washington Department of Fisheries (WDF), US Fish and Wildlife Service (FWS) and National Marine Fisheries Service (NMFS). Study objectives addressed by each agency are to describe the life history and population dynamics of subadults and adults between Bonneville and McNary dams and evaluate the need and identify potential methods for protecting, mitigating and enhancing populations downstream from McNary Dam, to describe the white sturgeon recreational fishery between Bonneville and McNary dams, describe reproductive and early life history characteristics downstream from Bonneville Dam and describe life history and population dynamics of subadults and adults downstream from Bonneville Dam, to describe reproduction and early life history characteristics, define habitat requirements for spawning and rearing and quantify extent of habitat available between Bonneville and McNary dams, and to describe reproduction and early life history characteristics, define habitat requirements for spawning and rearing and quantify extent of habitat available downstream from Bonneville Dam. Our approach is to work concurrently downstream and upstream from Bonneville Dam. Upstream from Bonneville Dam we began work in the Dalles Reservoir in 1987 and expanded efforts to Bonneville Reservoir in 1988 and John Day Reservoir in 1989. Highlights from this work is also included. 47 refs., 33 figs., 66 tabs.

Long-duration high-volume dam releases are unique anthropogenic events with no naturally occurring equivalents. The impact from such dam releases on a downstream Quaternary alluvial aquifer in New South Wales, Australia, is assessed. It is observed that long-duration (>26 days), high-volume dam releases (>8,000 ML/day average) result in significant variations in river-aquifer interactions. These variations include a flux from the river to the aquifer up to 6.3 m3/day per metre of bank (at distances of up to 330 m from the river bank), increased extent and volume of recharge/bank storage, and a long-term (>100 days) reversal of river-aquifer fluxes. In contrast, during lower-volume events (<2,000 ML/day average) the flux was directed from the aquifer to the river at rates of up to 1.6 m3/day per metre of bank. A groundwater-head prediction model was constructed and river-aquifer fluxes were calculated; however, predicted fluxes from this method showed poor correlation to fluxes calculated using actual groundwater heads. Long-duration high-volume dam releases have the potential to skew estimates of long-term aquifer resources and detrimentally alter the chemical and physical properties of phreatic aquifers flanking the river. The findings have ramifications for improved integrated management of dam systems and downstream aquifers.

Twenty-three measurement of discharge were used to determine discharge ratings for the five adjustable sluice gates, spillway and fish ladder at McHenry Dam on the Fox River in Illinois. Discharge ratings were determined for free weir, free orifice, and submerged orifice flow regimes. Hydraulic conditions that identify flow regimes at McHenry Dam are defined by ratios between headwater depth (h1), tailwater depth (h3), and gate opening (hg). Flow under the sluice gates is identified as weir flow when the ratio of gate opening to headwater depth is greater than 0.73, and as orifice flow when hg/H1 is less than 0.73. Free orifice flow occurs when the ratio of tailwater depth to gate opening is less than 1.3, and submerged orifice flow occurs when h3/hg is greater than 1.3. Flow under the sluice gates is identified as free weir flow when the ratio of tailwater depth to headwater depth is less than 0.75, and as submerged weir flow when h3/h1 is greater than 0.75. Flow over the spillway is identified as free weir flow when the ratio of tailwater depth to headwater depth is less than 0.60, and as submerged weir flow when h3/h1 is greater than 0.60. Discharge coefficients to be used in equations to compute discharge for various hydraulic conditions were determined. Four discharge measurement, ranging from 169 to 2990 cu ft/sec, were used to define discharge coefficients that varies from 2.61 to 3.14 for free weir flow over the spillway. Nineteen discharge measurements, ranging from 180 to 4050 cu ft/sec, were used to define discharge coefficients for free weir, free orifice, and submerged orifice flow under the sluice gates. The average value of the discharge coefficient for free weir flow under the sluice gates is 3.17. Discharge coefficients for free orifice flow varied from 0.48 to 0.66 and the discharge coefficients for submerged orifice flow from the two measurements were 0.59 and 0.67. (Author 's abstract)

Steelhead (Oncorhynchus mykiss) populations have declined throughout their range in the last century and many populations, including those of the Snake River Basin are listed under the Endangered Species Act of 1973. The reasons for their decline are many and complex, but include habitat loss and degradation, overharvesting, and dam construction. The 2008 Biological Opinion calls for an increase in the abundance of female steelhead through an increase in iteroparity (i.e., repeat spawning) and this can be realized through a combination of reconditioning and in-river survival of migrating kelts. The goal of this study is to provide the data necessary to inform fisheries managers and dam operators of Snake River kelt migration patterns, survival, and routes of dam passage. Steelhead kelts (n = 487) were captured and implanted with acoustic transmitters and passive integrated transponder (PIT)-tags at the Lower Granite Dam (LGR) Juvenile Fish Facility and at weirs located in tributaries of the Snake and Clearwater rivers upstream of LGR. Kelts were monitored as they moved downstream through the Federal Columbia River Power System (FCRPS) by 15 autonomous and 3 cabled acoustic receiver arrays. Cabled receiver arrays deployed on the dam faces allowed for three-dimensional tracking of fish as they approached the dam face and were used to determine the route of dam passage. Overall, 27.3% of the kelts tagged in this study successfully migrated to Martin Bluff (rkm 126, as measured from the mouth of the Columbia River), which is located downstream of all FCRPS dams. Within individual river reaches, survival per kilometer estimates ranged from 0.958 to 0.999; the lowest estimates were observed in the immediate forebay of FCRPS dams. Steelhead kelts tagged in this study passed over the spillway routes (spillway weirs, traditional spill bays) in greater proportions and survived at higher rates compared to the few fish passed through powerhouse routes (turbines and juvenile

Steelhead (Oncorhynchus mykiss) populations have declined throughout their range in the last century and many populations, including those of the Snake River Basin are listed under the Endangered Species Act of 1973. The reasons for their decline are many and complex, but include habitat loss and degradation, overharvesting, and dam construction. The 2008 Biological Opinion calls for an increase in the abundance of female steelhead through an increase in iteroparity (i.e., repeat spawning) and this can be realized through a combination of reconditioning and in-river survival of migrating kelts. The goal of this study is to provide the data necessary to inform fisheries managers and dam operators of Snake River kelt migration patterns, survival, and routes of dam passage. Steelhead kelts (n = 487) were captured and implanted with acoustic transmitters and passive integrated transponder (PIT)-tags at the Lower Granite Dam (LGR) Juvenile Fish Facility and at weirs located in tributaries of the Snake and Clearwater rivers upstream of LGR. Kelts were monitored as they moved downstream through the Federal Columbia River Power System (FCRPS) by 15 autonomous and 3 cabled acoustic receiver arrays. Cabled receiver arrays deployed on the dam faces allowed for three-dimensional tracking of fish as they approached the dam face and were used to determine the route of dam passage. Overall, 27.3% of the kelts tagged in this study successfully migrated to Martin Bluff (rkm 126, as measured from the mouth of the Columbia River), which is located downstream of all FCRPS dams. Within individual river reaches, survival per kilometer estimates ranged from 0.958 to 0.999; the lowest estimates were observed in the immediate forebay of FCRPS dams. Steelhead kelts tagged in this study passed over the spillway routes (spillway weirs, traditional spill bays) in greater proportions and survived at higher rates compared to the few fish passed through powerhouse routes (turbines and juvenile

Chinese sturgeon ( Acipenser sinensis) is the flagship species of the Changjiang River. The migration route of this species is blocked by the first dam, the Gezhou Dam, and its reproduction is affected by the Three Gorges Dam (TGD), one of the largest dams in the world. We studied the impact of the impoundment of the Three Gorges Reservoir (TGR) since 2003 on the spawning stock and the natural reproduction of the Chinese sturgeon by using our monitoring data from 1997 to 2013. Results indicate that TGR impoundment has delayed the first spawning dates of the fish from middle-late October to late November, decreased the amount of spawning activities from twice to only once each year, and significantly reduced egg production. In particular, the fish did not demonstrate any spawning activities in 2013. Therefore, TGR impoundment significantly affects the natural reproduction of the fish downstream of the TGD. The spawning stock size of the fish is also predicted to further decrease in the future, which will lead to a risk of population extinction. Ecological regulations must be imposed on decreasing the water temperature to 20°C before mid-October and increasing water discharge downstream of the TGD in October to induce spawning of the Chinese sturgeon.

Chinese sturgeon (Acipenser sinensis) is the flagship species of the Changjiang River. The migration route of this species is blocked by the first dam, the Gezhou Dam, and its reproduction is affected by the Three Gorges Dam (TGD), one of the largest dams in the world. We studied the impact of the impoundment of the Three Gorges Reservoir (TGR) since 2003 on the spawning stock and the natural reproduction of the Chinese sturgeon by using our monitoring data from 1997 to 2013. Results indicate that TGR impoundment has delayed the first spawning dates of the fish from middle-late October to late November, decreased the amount of spawning activities from twice to only once each year, and significantly reduced egg production. In particular, the fish did not demonstrate any spawning activities in 2013. Therefore, TGR impoundment significantly affects the natural reproduction of the fish downstream of the TGD. The spawning stock size of the fish is also predicted to further decrease in the future, which will lead to a risk of population extinction. Ecological regulations must be imposed on decreasing the water temperature to 20°C before mid-October and increasing water discharge downstream of the TGD in October to induce spawning of the Chinese sturgeon.

The specific research goal of this project is to identify means to restore and rebuild the Snake River white sturgeon (Acipenser transmontanus) population to support a sustainable annual subsistence harvest equivalent to 5 kg/ha/yr (CBFWA 1997). Based on data collected, a white sturgeon adaptive management plan will be developed. This 2000 annual report covers the fourth year of sampling of this multi-year study. In 2000 white sturgeon were captured, marked, and population data were collected in the Snake and Salmon rivers. The Snake River was sampled between Lower Granite Dam (rkm 174) and the mouth of the Salmon River (rkm 303), and the Salmon River was sampled from its mouth upstream to Hammer Creek (rkm 84). A total of 53,277 hours of setline effort and 630 hours of hook-and-line effort was employed in 2000. A total of 538 white sturgeon were captured and tagged in the Snake River and 25 in the Salmon River. Since 1997, 32.8 percent of the tagged white sturgeon have been recaptured. In the Snake River, white sturgeon ranged in total length from 48 cm to 271 cm and averaged 107 cm. In the Salmon River, white sturgeon ranged in total length from 103 cm to 227 cm and averaged 163 cm. Using the Jolly-Seber open population estimator, the abundance of white sturgeon <60 cm, between Lower Granite Dam and the mouth of the Salmon River, was estimated at 2,725 fish, with a 95% confidence interval of 1,668-5,783. A total of 10 white sturgeon were fitted with radio-tags. The movement of these fish ranged from 54.7 km (34 miles) downstream to 78.8 km (49 miles) upstream; however, 43.6 percent of the detected movement was less than 0.8 km (0.5 mile). Both radio-tagged fish and recaptured white sturgeon in Lower Granite Reservoir appear to move more than fish in the free-flowing segment of the Snake River. No seasonal movement pattern was detected, and no movement pattern was detected for different size fish. Differences were detected in the length frequency distributions of

Redd counts are routinely used to document the spawning distribution of fall Chinook salmon (Oncorhynchus tshawytscha) in the Snake River basin upriver of Lower Granite Dam. The first reported redd counts were from aerial searches conducted intermittently between 1959 and 1978 (Irving and Bjornn 1981, Witty 1988; Groves and Chandler 1996)(Appendix 1). In 1986, the Washington Department of Fish and Wildlife began an annual monitoring program that, in addition to the Snake River, included aerial searches of the Grande Ronde River the first year (Seidel and Bugert 1987), and the Imnaha River in subsequent years (Seidel et al. 1988; Bugert et al. 1989-1991; Mendel et al. 1992). The U. S. Fish and Wildlife Service and Idaho Power Company began contributing to this effort in 1991 by increasing the number of aerial searches conducted each year and adding underwater searches in areas of the Snake River that were too deep to be searched from the air (Connor et al. 1993; Garcia et al. 1994a, 1994b, 1996-2007; Groves 1993; Groves and Chandler 1996). The Nez Perce Tribe added aerial searches in the Clearwater River basin beginning in 1988 (Arnsberg et. al 1992), and the Salmon River beginning in 1992. Currently searches are conducted cooperatively by the Nez Perce Tribe, Idaho Power Company, and U. S. Fish and Wildlife Service. Our objective for this report was to consolidate the findings from annual redd searches counted upstream of Lower Granite Dam into a single document, containing detailed information about the searches from the most recent spawning season, and summary information from previous years. The work conducted in 2007 was funded by the Bonneville Power Administration and Idaho Power Company.

Accounting for the use of Colorado River water is required by the U.S. Supreme Court decree, 1964, Arizona v. California. Water pumped from wells on the flood plain and from certain wells on alluvial slopes outside the flood plain is presumed to be river water and is accounted for as Colorado River water. The accounting-surface method developed for the area upstream from Laguna Dam was modified for use downstream from Laguna Dam to identify wells outside the flood plain of the lower Colorado River that yield water that will be replaced by water from the river. Use of the same method provides a uniform criterion of identification for all users pumping water from wells by determining if the static water-level elevation in the well is above or below the elevation of the accounting surface. Wells that have a static water-level elevation equal to or below the accounting surface are presumed to yield water that will be replaced by water from the Colorado River. Wells that have a static water-level elevation above the accounting surface are presumed to yield river water stored above river level. The method is based on the concept of a river aquifer and an accounting surface within the river aquifer. The river aquifer consists of permeable sediments and sedimentary rocks that are hydraulically connected to the Colorado River so that water can move between the river and the aquifer in response to withdrawal of water from the aquifer or differences in water-level elevations between the river and the aquifer. The subsurface limit of the river aquifer is the nearly impermeable bedrock of the bottom and sides of the basins that underlie the Yuma area and adjacent valleys. The accounting surface represents the elevation and slope of the unconfined static water table in the river aquifer outside the flood plain of the Colorado River that would exist if the river were the only source of water to the river aquifer. The accounting surface was generated by using water

The Santa Ana River, located in an extensively urbanized basin, drains about 2,670 square miles near Los Angeles, California. Almost all flow in the river, about 200,000 acre-feet annually, is diverted to ponds where it infiltrates and recharges underlying aquifers. About 2 million people are dependent on these aquifers for water supply. In recent years, base flow in the river has increased as a result of increased discharge of treated municipal wastewater, and high flows have increased as a result of increase precipitation and urbanization. Trends in water quality were calculated for two sites?at the Metropolitan Water District (MWD) Crossing (an upstream site) and below Prado Dam (a downstream site)?using the computer program ESTREND. Water-quality data for these sites were collected by the U.S. Geological Survey from 1969 to 1995. At MWD Crossing, flow-adjusted downward trends of -1.1 microsiemens per centimeter (iS/cm) per year and -1.6 milligrams per liter (mg/L) per year were calculated for specific conductance and dissolved solids, respectively. In contrast, a flow-adjusted upward trends of 2.2 iS/cm per year for dissolved solids was calculated for the Santa Ana River below Prado Dam. Specific conductance and dissolved solids in the Santa Ana River below Prado Dam had downward unadjusted trends (not adjusted for streamflow) of -8.3 iS/cm per year and -6.0 mg/L per year, respectively. For the Santa Ana River below Prado Dam, downward unadjusted trends were calculated for ammonia (-0.04 mg/L per year) and total organic carbon (0.19 mg/L per year); flow-adjusted upward trends were calculated for nitrite plus nitrate (0.15 mg/L per year), total dissolved nitrogen (0.39 mg/L per year), and orthophosphate (0.03 mg/L per year). Statistically significant unadjusted and flow-adjusted trends were not obtained for organic nitrogen, phosphorus, and dissolved organic carbon. Data for selected trace elements and organic compounds collected between 1970-94 also are

This learning packet provides background information about Hoover Dam (Nevada) and the surrounding area. Since the dam was built at the height of the Depression in 1931, people came from all over the country to work on it. Because of Hoover Dam, the Colorado River was controlled for the first time in history and farmers in Nevada, California, and…

High specific discharges from Himalayan headwater basins feed major reservoirs generating hydropower and supplying water to irrigation schemes across the Punjab plains of north-west India and Pakistan. Flow arises from seasonal winter snow cover, summer monsoon precipitation and melting glacier ice in varying proportions and differing absolute quantities along west -east axes of the Karakoram and western Himalaya. Discharge records for stations above Tarbela (Indus), Mangla (Jhelum), Marala (Chenab) and Bhakra (Sutlej) dams have been examined for periods between 1920 and 2009, together with precipitation and air temperature data for stations with long records (within the period 1893 to 2013) at elevations between 234 and 3015 m a.s.l. Ice-cover age in the basins above the dams was between 1 and 12 %. Flows in the Sutlej, Chenab and Jhelum reached maxima in the 1950s before declining to the 1970s. Flow in the Chenab and Jhelum increased to 1950s levels in the 1990s, before falling steeply into the 2000s mimicking variations in winter and monsoon precipitation. Discharge in the Indus at Tarbela increased from the 1970s, reaching a maximum in the late 1980s/early 1990s, before declining back to 1970s levels in the 2000s, flow being influenced not only by precipitation fluctuations but also by changes in air temperature affecting glacier melt in headwater basins. Runoff at Bhakra was augmented by flow from the Beas-Sutlej link canal after 1977, but natural flow in the Sutlej above Luhri reduced considerably from the 1990s influenced by declining flows in the relatively dry but large Tibetan portion of the basin area. Large year-to-year fluctuations of reservoir inflows are nonetheless based on significant sustained underlying discharge levels at all four reservoirs.

Lancang-Mekong River Basin is one of ecoregions with rich biodiversity and high ecological values in the world. The basin has been strongly affected by human activities, particularly by dam construction. This study was conducted to investigate the vegetation distribution patterns in the dam areas along middle-low reach of the Lancang-Mekong River in Yunnan Province of China, where eight cascade dams have been planned or are being constructed. To identify the vegetation composition and structure, we sampled 126 quadrats along the transects arrayed vertically to both side of river channel from the year of 2004 to 2010. We found that the forest, shrub and grass communities were widely spread along the riverside. In low reach watershed of the Lancang-Mekong River, the dominated vegetations were grasses and shrubs which were severely disturbed by human activity. In middle reach of the Lancang-Mekong River, the dry-hot valley vegetation was found in the low valley. At high altitude, the pine forest and semi-evergreen seasonal forest were found. As a result of dam construction and operation, the structure and compositions of riparian vegetation were strongly changed. Some plants declined or disappeared due to the alteration of their habitats. The protection or restoration interventions are urgently needed to mitigate the risk of vegetation damage associated with dam projects along middle and low reach of the Lancang-Mekong River.

Efforts are underway to identify actions that would improve water quality in the Link River to Keno Dam reach of the Upper Klamath River in south-central Oregon. To provide further insight into water-quality improvement options, three scenarios were developed, run, and analyzed using previously calibrated CE-QUAL-W2 hydrodynamic and water-quality models. Additional scenarios are under development as part of this ongoing study. Most of these scenarios evaluate changes relative to a "current conditions" model, but in some cases a "natural conditions" model was used that simulated the reach without the effect of point and nonpoint sources and set Upper Klamath Lake at its Total Maximum Daily Load (TMDL) targets. These scenarios were simulated using a model developed by the U.S. Geological Survey (USGS) and Watercourse Engineering, Inc. for the years 2006–09, referred to here as the "USGS model." Another model of the reach was developed by Tetra Tech, Inc. for years 2000 and 2002 to support the Klamath River TMDL process; that model is referred to here as the "TMDL model." The three scenarios described in this report included (1) an analysis of whether this reach of the Upper Klamath River would be in compliance with dissolved oxygen standards if sources met TMDL allocations, (2) an application of more recent datasets to the TMDL model with comparison to results from the USGS model, and (3) an examination of the effect on dissolved oxygen in the Klamath River if particulate material were stopped from entering Klamath Project diversion canals. Updates and modifications to the USGS model are in progress, so in the future these scenarios will be reanalyzed with the updated model and the interim results presented here will be superseded. Significant findings from this phase of the investigation include: * The TMDL analysis used depth-averaged dissolved oxygen concentrations from model output for comparison with dissolved oxygen standards. The Oregon dissolved oxygen

Reservoirs on rivers can disrupt organic carbon (OC) transport and transformation, but less is known how downstream river reaches directly below dams contribute to OC processing than reservoirs alone. We compared how reservoirs and their associated tailwaters affected OC quantity and quality by calculating particulate (P) OC and dissolved (D) OC fluxes, and measuring composition and bioavailability of DOC. We sampled the Yampa River near Maybell, Colorado, USA and the Green River above and below Fontenelle and Flaming Gorge reservoirs, and their respective tailwaters from early snowmelt to base flow hydrological conditions. In unregulated reaches (Yampa River, Green River above Fontenelle reservoir), DOC and POC concentrations increased with snowmelt discharge. POC and DOC concentrations also increased with stream discharge below Fontenelle reservoir, but there was no relationship between DOC and stream flow below Flaming Gorge reservoir. The annual load of POC was 3-fold lower below Fontenelle Reservoir and nearly 7-fold lower below Flaming Gorge reservoir, compared to their respective upstream sampling sites. DOC exported to downstream reaches from both reservoirs was less bioavailable, as measured with bioassays, than DOC upriver of the reservoirs. Lastly, tailwater reaches below the reservoirs generated OC, exporting 1.6-2.2 g C m-2 d-1 of OC to downstream ecosystems. Changes in total fluxes from upstream to downstream of reservoirs and their tailwaters do not represent the simultaneous transformation and production of OC, which may lead to the underestimation of the quantity of OC mineralized, transformed, or retained in coupled river-reservoir-tailwater ecosystems.

The specific research goal of this project is to identify means to restore and rebuild the Snake River white sturgeon (Acipenser transmontanus) population to support a sustainable annual subsistence harvest equivalent to 5 kg/ha/yr (CBFWA 1997). Based on data collected, a white sturgeon adaptive management plan will be developed. This 2001 annual report covers the fifth year of sampling of this multi-year study. In 2001 white sturgeon were captured, marked, and population data were collected in the Snake and Salmon rivers. The Snake River was sampled between Lower Granite Dam (rkm 174) and the mouth of the Salmon River (rkm 303), and the Salmon River was sampled from its mouth upstream to Hammer Creek (rkm 84). A total of 45,907 hours of setline effort and 186 hours of hook-and-line effort was employed in 2001. A total of 390 white sturgeon were captured and tagged in the Snake River and 12 in the Salmon River. Since 1997, 36.1 percent of the tagged white sturgeon have been recaptured. In the Snake River, white sturgeon ranged in total length from 42 cm to 307 cm and averaged 107 cm. In the Salmon River, white sturgeon ranged in total length from 66 cm to 235 cm and averaged 160 cm. Using the Jolly-Seber model, the abundance of white sturgeon <60 cm, between Lower Granite Dam and the mouth of the Salmon River, was estimated at 2,483 fish, with a 95% confidence interval of 1,208-7,477. An additional 10 white sturgeon were fitted with radio-tags during 2001. The locations of 17 radio-tagged white sturgeon were monitored in 2001. The movement of these fish ranged from 38.6 km (24 miles) downstream to 54.7 km (34 miles) upstream; however, 62.6 percent of the detected movement was less than 0.8 km (0.5 mile). Both radio-tagged fish and recaptured white sturgeon in Lower Granite Reservoir appear to move more than fish in the free-flowing segment of the Snake River. No seasonal movement pattern was detected, and no movement pattern was detected for different size fish

The fragmentation of lotic systems caused by construction of dams has modified many aquatic communities. The objective of this study was to analyse changes in the aquatic insect community structure by discontinuity of habitat created by dams along the Ribeirão das Anhumas, a sub-basin of the Mogi-Guaçu River (state of São Paulo, Brazil). Entomofauna collection was carried out in 10 segments upstream and downstream of five dams along the longitudinal profile of the stream, with a quick sampling method using a D net (mesh 250 mm) with 2 minutes of sampling effort. The insects were sorted and identified to the lowest possible taxonomic level and analysed by the Shannon diversity index, β diversity, richness estimated by rarefaction curves and relative participation of functional feeding groups. The results showed a slight reduction in diversity in the downstream segments, as well as along the longitudinal profile of the stream. However, there were no significant differences in abundance and richness between the upstream and downstream segments, indicating that the dams did not influence these variables. Differences were observed in the functional feeding groups along the longitudinal profile. Predator and gatherer insects were dominant in all segments analysed. The feeding group of shredders was more abundant in the segment DSIII with the participation of Marilia Müller (Odontoceridae - Trichoptera), although we observed a decrease of shredders and scrapers with the decrease of the canopy cover reducing values of β diversity in the continuum of Ribeirão das Anhumas. This result demonstrated the importance of the conservation of the riparian vegetation in order to maintain the integrity of the stream. PMID:25055089

Diversion dams can negatively affect emigrating juvenile salmon populations because fish must pass through the impounded river created by the dam, negotiate a passage route at the dam and then emigrate through a riverine reach that has been affected by reduced river discharge. To quantify the effects of a main-stem diversion dam on juvenile Chinook salmon in the Yakima River, Washington, USA, we used radio telemetry to understand how dam operations and river discharge in the 18-km reach downstream of the dam affected route-specific passage and survival. We found evidence of direct mortality associated with dam passage and indirect mortality associated with migration through the reach below the dam. Survival of fish passing over a surface spill gate (the west gate) was positively related to river discharge, and survival was similar for fish released below the dam, suggesting that passage via this route caused little additional mortality. However, survival of fish that passed under a sub-surface spill gate (the east gate) was considerably lower than survival of fish released downstream of the dam, with the difference in survival decreasing as river discharge increased. The probability of fish passing the dam via three available routes was strongly influenced by dam operations, with passage through the juvenile fish bypass and the east gate increasing with discharge through those routes. By simulating daily passage and route-specific survival, we show that variation in total survival is driven by river discharge and moderated by the proportion of fish passing through low-survival or high-survival passage routes.

The McClellan-Kerr Arkansas River Navigation System (MKARNS), completed in 1971, required the construction of 17 locks and dams and associated navigation works to make the Arkansas and Verdigris Rivers navigable for barge traffic from the Mississippi River to Catoosa, Oklahoma. We used a Geographic Information System to assess habitat changes in the 477-km portion of this system within Arkansas from 1973 to 1999. Total aquatic area declined by 9% from 42 404 to 38 655 ha. Aquatic habitat losses were 1-17% among pools. Greatest habitat losses occurred in diked secondary channels (former secondary channels with flow reduced by rock dikes) and backwaters adjacent to the main channel. Most of the area of dike pools (aquatic habitat downstream of rock dikes), diked secondary channels and adjacent backwaters were <0.9 m deep. Copyright ?? 2008 John Wiley & Sons, Ltd.

The restoration of salmonids in the Elwha River following dam removal will cause interactions between anadromous and potamodromous forms as recolonization occurs in upstream and downstream directions. Anadromous salmonids are expected to recolonize historic habitats, and rainbow trout (Oncorhynchus mykiss) and bull trout (Salvelinus confluentus) isolated above the dams for 90 years are expected to reestablish anadromy. We summarized the distribution and abundance of potamodromous salmonids, determined locations of spawning areas, and mapped natural barriers to fish migration at the watershed scale based on data collected from 1993 to 2006. Rainbow trout were far more abundant than bull trout throughout the watershed and both species were distributed up to river km 71. Spawning locations for bull trout and rainbow trout occurred in areas where we anticipate returning anadromous fish to spawn. Nonnative brook trout were confined to areas between and below the dams, and seasonal velocity barriers are expected to prevent their upstream movements. We hypothesize that the extent of interaction between potamodromous and anadromous salmonids will vary spatially due to natural barriers that will limit upstream-directed recolonization for some species of salmonids. Consequently, most competitive interactions will occur in the main stem and floodplain downstream of river km 25 and in larger tributaries. Understanding future responses of Pacific salmonids after dam removal in the Elwha River depends upon an understanding of existing conditions of the salmonid community upstream of the dams prior to dam removal.

The regulation of flow of the Colorado River by Glen Canyon Dam began in 1963. This resulted in significant changes to the downstream ecosystem of the Colorado River in Grand Canyon, contributing to the initiation of the Glen Canyon Environmental Studies program in 1982, followed by establishment of the Glen Canyon Dam Adaptive Management Program in 1996. This report describes a water-temperature dataset collected through these programs for the reach of the Colorado River and selected tributaries between Glen Canyon Dam and Spencer Canyon (approximately 261 river miles) in northern Arizona from 1988 to 2005. The primary purposes of the report are to summarize the methods of data collection, processing, and editing; to present summary statistics; and to make the data described in the report available.

In 2007, Marmot Dam on the Sandy River, Oregon, was removed and a temporary cofferdam standing in its place was breached, allowing the river to flow freely along its entire length. Time-lapse imagery obtained from a network of digital single-lens reflex cameras placed around the lower reach of the sediment-filled reservoir behind the dam details rapid erosion of sediment by the Sandy River after breaching of the cofferdam. Within hours of the breaching, the Sandy River eroded much of the nearly 15-m-thick frontal part of the sediment wedge impounded behind the former concrete dam; within 24-60 hours it eroded approximately 125,000 m3 of sediment impounded in the lower 300-meter-reach of the reservoir. The imagery shows that the sediment eroded initially through vertical incision, but that lateral erosion rapidly became an important process.

Around 11.5 ∗ 106 m3 of rock detached from the eastern slope of the Santa Cruz valley (San Juan province, Argentina) in the first fortnight of January 2005. The rockslide-debris avalanche blocked the course, resulting in the development of a lake with maximum length of around 3.5 km. The increase in the inflow rate from 47,000-74,000 m3/d between April and October to 304,000 m3/d between late October and the first fortnight of November, accelerated the growing rate of the lake. On 12 November 2005 the dam failed, releasing 24.6 ∗ 106 m3 of water. The resulting outburst flood caused damages mainly on infrastructure, and affected the facilities of a hydropower dam which was under construction 250 km downstream from the source area. In this work we describe causes and consequences of the natural dam formation and failure, and we dynamically model the 2005 rockslide-debris avalanche with DAN3D. Additionally, as a volume ~ 24 ∗ 106 m3of rocks still remain unstable in the slope, we use the results of the back analysis to forecast the formation of a future natural dam. We analyzed two potential scenarios: a partial slope failure of 6.5 ∗ 106 m3 and a worst case where all the unstable volume remaining in the slope fails. The spreading of those potential events shows that a new blockage of the Santa Cruz River is likely to occur. According to their modeled morphometry and the contributing watershed upstream the blockage area, as the one of 2005, the dams would also be unstable. This study shows the importance of back and forward analysis that can be carried out to obtain critical information for land use planning, hazards mitigation, and emergency management.

Sedimentary material from coastal and nearshore areas in the Mississippi Delta region are comprised of different organic carbon sources with diverse ages that require isotopic and elemental records for resolving the various sources of plant residues. Carbon isotopic ((13)C, (14)C) values were used to differentiate contributions from plants using the C3, C4, and/or CAM (crassulacean acid metabolism) carbon fixation pathways., and iodine concentrations indicated that wetland plant residues are a significant source of organic carbon in a sediment core from the Mississippi River delta region collected at a 60 m water depth. This sediment core had been extensively described in Oktay et al. [Oktay, S.D., Santschi, P.H., Moran, J.E., Sharma, P., 2000. The (129)Iodine Bomb Pulse Recorded in Mississippi River delta Sediments: Results from Isotopes of I, Pu, Cs, Pb, and C. Geochim. Cosmochim. Acta 64 (6), 989-996.] and significantly, includes unique features that had not previously been seen in the marine environment. These special features include a plutonium isotopic close-in fallout record that indicates a purely terrestrial source for these sediment particles and the elements associated with it, and a distinct iodine isotopic peak (as well as peaks for plutonium and cesium isotopes) that indicate little bioturbation in this core. Our carbon isotopic and iodine data can thus be compared to published records of changes in drainage basin land use, river hydrology, and hydrodynamic sorting of suspended particles to elucidate if these changes are reflected in nearshore sediments. This comparison suggests a significant contribution for organic carbon (OC) from C4 plants to these sediments during the 1950's to early 1960's. Relative older carbon isotopes, and episodically high iodine concentrations (up to 34 ppm) were observed during this time period that (1) indicate sediment deposition that is coincident with the times of major hydrological changes induced from dam and levee

The declining population of Kootenai River white sturgeon, which was listed as an Endangered Species in 1994, has prompted a recovery team to assess the feasibility of various habitat enhancement scenarios to reestablish white sturgeon populations. As the first phase in this assessment, the U.S. Geological Survey collected stream channel cross-section and longitudinal data during 2002—03 at about 400 locations along the Kootenai River from Libby Dam near Libby, Montana, to where the river empties into Kootenay Lake near Creston, British Columbia, Canada. Survey control stations with a horizontal and vertical accuracy of less than 0.1 foot were established using a global positioning system (GPS) prior to collection of stream channel cross-section data along the Kootenai River. A total of 245 cross sections were surveyed. Six cross sections upstream from Kootenai Falls were surveyed using a total station where the river was too shallow or dangerous to navigate by vessel. The remaining 239 cross sections were surveyed by interfacing real-time GPS equipment with an echo sounder to obtain bathymetric data and with a laser range- finder to obtain streambank data. These data were merged, straightened, ordered, and reduced in size to be useful. Spacing between these cross sections ranged from about 600 feet in the valley flat near Deep Creek and Shorty Island and near bridges to as much as several miles in other areas. These stream channel cross sections will provide information that can be used to develop hydraulic flow models of the Kootenai River from Libby Dam, Montana, to Queens Bay on Kootenay Lake in British Columbia, Canada.

Damming the natural flow regime is responsible to drive away native species from the aquatic ecosystem and it becomes potentially damaging when it concerns the drought-prone areas in particular. Drought cycles are common in the Great Plains, which have given native fish species adapted strategies for coping with extreme variation in flow regimes. However, native populations have crashed as these stream networks became heavily fragmented beginning in the post-depression water reclamation era and continued into the 1960's boom in flood control dam construction. This study is an attempt to understand and assess the cumulative impacts of river network fragmentation and climate change on the river ecosystem, geomorphology and hydrology of the Smoky-Hill River Basin of North-West Kansas. The vast majority of the basin does not overly significant groundwater resources and is thus reliant on water supplied from precipitation, runoff, and shallow alluvial storage zones strongly connected to surface water systems, which is now fragmented by the construction of both small farm-ponds as well as big flood reservoir structures. Thus, there is a high probability of stream network segments to be dissociated (from the main channel during dry periods) and/or completely depleted (in case of a series of drought cycles) in this area. This paper would identify such vulnerable network segments and assess the impact of extreme climatic conditions - as a single event or scenario of cyclic droughts that can drive the native fishes out of the Smoky-Hill River Basin - by comparing modeled future flow regime projections with historic flow regimes in the fragmented river structure. The study will further address structural and functional connectivity of the river and would contribute to the understanding of fragmentation and its effect to the stream ecology at a higher scale, where a larger aquatic population can get affected by a single drought event.

Longitudinal connectivity is a fundamental characteristic of rivers that can be disrupted by natural and anthropogenic processes. Dams are significant disruptions to streams. Over 2,000,000 low-head dams (<7.6 m high) fragment United States rivers. Despite potential adverse impacts of these ubiquitous disturbances, the spatial impacts of low-head dams on geomorphology and ecology are largely untested. Progress for research and conservation is impaired by not knowing the magnitude of low-head dam impacts. Based on the geomorphic literature, we refined a methodology that allowed us to quantify the spatial extent of low-head dam impacts (herein dam footprint), assessed variation in dam footprints across low-head dams within a river network, and identified select aspects of the context of this variation. Wetted width, depth, and substrate size distributions upstream and downstream of six low-head dams within the Upper Neosho River, Kansas, United States of America were measured. Total dam footprints averaged 7.9 km (3.0-15.3 km) or 287 wetted widths (136-437 wetted widths). Estimates included both upstream (mean: 6.7 km or 243 wetted widths) and downstream footprints (mean: 1.2 km or 44 wetted widths). Altogether the six low-head dams impacted 47.3 km (about 17%) of the mainstem in the river network. Despite differences in age, size, location, and primary function, the sizes of geomorphic footprints of individual low-head dams in the Upper Neosho river network were relatively similar. The number of upstream dams and distance to upstream dams, but not dam height, affected the spatial extent of dam footprints. In summary, ubiquitous low-head dams individually and cumulatively altered lotic ecosystems. Both characteristics of individual dams and the context of neighboring dams affected low-head dam impacts within the river network. For these reasons, low-head dams require a different, more integrative, approach for research and management than the individualistic approach

Longitudinal connectivity is a fundamental characteristic of rivers that can be disrupted by natural and anthropogenic processes. Dams are significant disruptions to streams. Over 2,000,000 low-head dams (<7.6 m high) fragment United States rivers. Despite potential adverse impacts of these ubiquitous disturbances, the spatial impacts of low-head dams on geomorphology and ecology are largely untested. Progress for research and conservation is impaired by not knowing the magnitude of low-head dam impacts. Based on the geomorphic literature, we refined a methodology that allowed us to quantify the spatial extent of low-head dam impacts (herein dam footprint), assessed variation in dam footprints across low-head dams within a river network, and identified select aspects of the context of this variation. Wetted width, depth, and substrate size distributions upstream and downstream of six low-head dams within the Upper Neosho River, Kansas, United States of America were measured. Total dam footprints averaged 7.9 km (3.0–15.3 km) or 287 wetted widths (136–437 wetted widths). Estimates included both upstream (mean: 6.7 km or 243 wetted widths) and downstream footprints (mean: 1.2 km or 44 wetted widths). Altogether the six low-head dams impacted 47.3 km (about 17%) of the mainstem in the river network. Despite differences in age, size, location, and primary function, the sizes of geomorphic footprints of individual low-head dams in the Upper Neosho river network were relatively similar. The number of upstream dams and distance to upstream dams, but not dam height, affected the spatial extent of dam footprints. In summary, ubiquitous low-head dams individually and cumulatively altered lotic ecosystems. Both characteristics of individual dams and the context of neighboring dams affected low-head dam impacts within the river network. For these reasons, low-head dams require a different, more integrative, approach for research and management than the individualistic

Longitudinal connectivity is a fundamental characteristic of rivers that can be disrupted by natural and anthropogenic processes. Dams are significant disruptions to streams. Over 2,000,000 low-head dams (<7.6 m high) fragment United States rivers. Despite potential adverse impacts of these ubiquitous disturbances, the spatial impacts of low-head dams on geomorphology and ecology are largely untested. Progress for research and conservation is impaired by not knowing the magnitude of low-head dam impacts. Based on the geomorphic literature, we refined a methodology that allowed us to quantify the spatial extent of low-head dam impacts (herein dam footprint), assessed variation in dam footprints across low-head dams within a river network, and identified select aspects of the context of this variation. Wetted width, depth, and substrate size distributions upstream and downstream of six low-head dams within the Upper Neosho River, Kansas, United States of America were measured. Total dam footprints averaged 7.9 km (3.0–15.3 km) or 287 wetted widths (136–437 wetted widths). Estimates included both upstream (mean: 6.7 km or 243 wetted widths) and downstream footprints (mean: 1.2 km or 44 wetted widths). Altogether the six low-head dams impacted 47.3 km (about 17%) of the mainstem in the river network. Despite differences in age, size, location, and primary function, the sizes of geomorphic footprints of individual low-head dams in the Upper Neosho river network were relatively similar. The number of upstream dams and distance to upstream dams, but not dam height, affected the spatial extent of dam footprints. In summary, ubiquitous low-head dams individually and cumulatively altered lotic ecosystems. Both characteristics of individual dams and the context of neighboring dams affected low-head dam impacts within the river network. For these reasons, low-head dams require a different, more integrative, approach for research and management than the individualistic

Three high-flow experiments (HFEs) were conducted by the U.S. Department of the Interior at Glen Canyon Dam, Arizona, in March 1996, November 2004, and March 2008. These experiments, also known as artificial or controlled floods, were large-volume, scheduled releases of water from Glen Canyon Dam that were designed to mimic some aspects of pre-dam Colorado River seasonal flooding. The goal of these experiments was to determine whether high flows could be used to benefit important physical and biological resources in Glen Canyon National Recreation Area and Grand Canyon National Park that had been affected by the operation of Glen Canyon Dam. Efforts such as HFEs that seek to maintain and restore downstream resources are undertaken by the U.S. Department of the Interior under the auspices of the Grand Canyon Protection Act of 1992 (GCPA; title XVIII, secs. 1801-1809, of Public Law 102-575). Scientists conducted a wide range of monitoring and research activities before, during, and after the experiments. Initially, research efforts focused on whether HFEs could be used to rebuild and maintain Grand Canyon sandbars, which provide camping beaches for hikers and whitewater rafters, create habitats potentially used by native fish and other wildlife, and are the source of windborne sand that may help to protect some archaeological resources from weathering and erosion. As scientists gained a better understanding of how HFEs affect the physical environment, research efforts expanded to include additional investigations about the effects of HFEs on biological resources, such as native fishes, nonnative sports fishes, riverside vegetation, and the aquatic food web. The chapters that follow summarize and synthesize for decisionmakers and the public what has been learned about HFEs to provide a framework for implementing similar future experiments. This report is a product of the Glen Canyon Dam Adaptive Management Program (GCDAMP), a Federal initiative authorized to ensure

Channel incision is a common occurrence in semi-arid regions of the Columbia River basin and throughout the world, where a fragile balance between climate, vegetation and geology makes channels susceptible to changes in hillslope erosion, stream discharge and sediment yield. Incision is defined as a rapid downcutting and lowering of the stream bed such that it reduces the frequency and duration of flooding onto the adjacent floodplain. We are studying the feasibility of restoring incised streams throughout the interior Columbia River basin. We hypothesize that under proper land use management, it is possible for them to aggrade such that they reconnect to their former floodplains within relatively short time frames. Theoretical and empirical evidence suggests that over decadal time scales, changes to land management that excludes grazing and allows riparian vegetation to become established can cause significant fill within the incised valleys. Preliminary modeling suggests that factors most affecting the length of time for an incised valley to completely aggrade and reconnect to its pre-incision floodplain are the depth of the incision, sediment production in the watershed, the amount and type of riparian vegetation, and the extent of beaver dam construction. While most natural resource and fisheries managers are aware of widespread incision throughout the Columbia River basin, the extent of incision within the range of the Pacific salmon is largely undocumented. However, we do know many incised streams that historically supported salmon no longer do so, and that habitat conditions are severely degraded in these incised streams. The historical record shows that numerous salmon-bearing streams in the semi-arid region of the interior Columbia River basin once contained narrow and deep, slowly meandering channels lined with cottonwoods, willows and/or sedges, contained numerous beaver dams, contained abundant and easily accessible off-channel habitat on the floodplain

Active restoration approaches such as channel reconstruction have moved beyond the realm of small streams and are being applied to larger rivers. Uncertainties arising from limited knowledge, fluvial and ecosystem variability, and contaminants are especially significant in restoration of large rivers, where project costs and the social, infrastructural, and ecological costs of failure are high. We use the case of Milltown Dam removal on the Clark Fork River, Montana and subsequent channel reconstruction in the former reservoir to examine the use of historical research and uncertainty analysis in river restoration. At a cost of approximately $120 million, the Milltown Dam removal involves the mechanical removal of approximately 2 million cubic meters of sediments contaminated by upstream mining, followed by restoration of the former reservoir reach in which a single-thread meandering channel is being constructed. Historical maps, surveys, photographs, and accounts suggest a conceptual model of a multi-thread, anastomosing river in the reach targeted for channel reconstruction, upstream of the confluence of the Clark Fork and Blackfoot Rivers. We supplemented historical research with analysis of aerial photographs, topographic data, and USGS stage-discharge measurements in a lotic but reservoir-influenced reach of the Clark Fork River within our study area to estimate avulsion frequency (0.8 avulsions/year over a 70-year period) and average rates of lateral migration and aggradation. These were used to calculate the mobility number, a dimensionless relationship between channel filling and lateral migration timescales that can be used to predict whether a river’s planform is single or multi-threaded. The mobility number within our study reach ranged from 0.6 (multi-thread channel) to 1.7 (transitional channel). We predict that, in the absence of active channel reconstruction, the post-dam channel pattern would evolve to one that alternates between single and multi

At approximately 9 p.m. on December 25, 1980, intense rainfall and extremely wet antecedent conditions combined to trigger a landslide of approximately 5,000 cubic yards at the head of Polallie Creek Canyon on the northeast flank of Mount Hood. The landslide was transformed rapidly into a debris flow, which surged down the channel at velocities between about 40 and 50 ft/s, eroding and incorporating large volumes of channel fill and uprooted vegetation. When it reached the debris fan at the confluence with the East Fork Hood River, the debris flow deposited approximately 100,000 cubic yards of saturated, poorly sorted debris to a maximum thickness of 35 ft, forming a 750-ft-long temporary dam across the channel. Within approximately 12 minutes, a lake of 85 acre-feet formed behind the blockage, breached the dam, and sent a flood wave down the East Fork Hood River. The combined debris flow and flood resulted in one fatality and over $13 million in damage to a highway, bridges, parks, and a water-supply pipeline. Application of simple momentum- and energy-balance equations, and uniform flow equations resulted in debris flow peak discharges ranging from 50,000 ft3/s to 300,000 ft3/s at different locations in the Polallie Creek Canyon. This wide range is attributed to temporary damming at the boulder- and log-rich flow front in narrow, curving reaches of the channel. When the volume of the solid debris was subtracted out, assuming a minimum peak debris-flow discharge of 100,000 ft3/s at the canyon mouth, a minimum peak-water discharge of 40,000 ft3/s was obtained. A computer dam-break model simulated peak flow for the outbreak flood on the East Fork Hood River in the range of 20,000 to 30,000 ft3/s using various breach shapes and durations of breach between 5 and 15 minutes. A slope conveyance computation 0.25 mi downstream from the dam gave a peak water discharge (solids subtracted out) for the debris-laden flood of 12,000 to 20,000 ft3/s, depending on the channel

Compagnie Nationale du Rhône (CNR) has been granted the concession to operate the Rhone River from the Swiss border to the Mediterranean Sea since 1933 and carries out three interdependent missions: navigation, irrigation and hydropower production. Nowadays, CNR generates one quarter of France's hydropower electricity. The convergence of public and private interests around optimizing the management of water resources throughout the French Rhone valley led CNR to develop hydrological models dedicated to discharge seasonal forecasting. Indeed, seasonal forecasting is a major issue for CNR and water resource management, in order to optimize long-term investments of the produced electricity, plan dam maintenance operations and anticipate low water period. Seasonal forecasting models have been developed on the Genissiat dam. With an installed capacity of 420MW, Genissiat dam is the first of the 19 CNR's hydropower plants. Discharge forecasting at Genissiat dam is strategic since its inflows contributes to 20% of the total Rhone average discharge and consequently to 40% of the total Rhone hydropower production. Forecasts are based on hydrological statistical models. Discharge on the main Rhone River tributaries upstream Genissiat dam are forecasted from 1 to 6 months ahead thanks to multiple linear regressions. Inputs data of these regressions are identified depending on river hydrological regimes and periods of the year. For the melting season, from spring to summer, snow water equivalent (SWE) data are of major importance. SWE data are calculated from Crocus model (Météo France) and SLF's model (Switzerland). CNR hydro-meteorological forecasters assessed meteorological trends regarding precipitations for the next coming months. These trends are used to generate stochastically precipitation scenarios in order to complement regression data set. This probabilistic approach build a decision-making supports for CNR's water resource management team and provides them with

1. GORGE HIGH DAM. THIS THIN ARCH DAM WITH A GRAVITY SECTION IS THE THIRD DAM BUILT BY SEATTLE CITY LIGHT TO PROVIDE WATER FOR GORGE POWERHOUSE AND WAS COMPLETED IN 1961, 1989. - Skagit Power Development, Gorge High Dam, On Skagit River, 2.9 miles upstream from Newhalem, Newhalem, Whatcom County, WA

Over the past 10 years in the U.S., dam removal has evolved from an occasionally implemented, rarely studied, and poorly understood intervention to improve rivers, to a much more frequently accomplished and better studied and understood approach to river restoration. Over that same time period, the numbers and sizes of dams and volumes of sediment released have dramatically increased. By some estimates close to 1000 dams have been removed over the last 100 years, with most of those occurring within the last 10. While most of these are small (less than 15 m high) dams, removals of dams up to 70 m high are presently underway. Releases of sediment associated with these removals over the past 10 years have also increased by close to four orders of magnitude; for example removal of the Elwha Riverdams in Washington is estimated to release almost 107 m3 of sediment into the lower Elwha River. Given a decade's worth of dam removals and, in some cases, well-orchestrated case studies of the effects of removal on the geomorphology and (to a lesser extent) ecology of rivers, what have we learned? More specifically, where do we now stand with respect to being able to predict the consequences of future dam removals? Drawing on both field examples and numerical models of dam removals in the western U.S., several key lessons stand out. Although every dam removal and river are different, removals initiate very rapid upstream river response and reservoir erosion and evacuation of sediment by various mechanisms that are strongly controlled by grain size of the deposit, volumes of residual sediment relative to total reservoir volume, and style of dam removal (instantaneous versus staged). Erosion of sediment accumulations in fully and partially filled (by sediment) reservoirs proceeds by different trajectories and rates, with full reservoirs releasing sediment primarily by upstream knickpoint retreat while erosion and sediment release in partially-filled reservoirs proceeds by

We report on our progress from April 2000 through March 2001 on determining the effects of mitigative measures on productivity of white sturgeon populations in the Columbia River downstream from McNary Dam, and on determining the status and habitat requirements of white sturgeon populations in the Columbia and Snake rivers upstream from McNary Dam. The study is a cooperative effort by the Oregon Department of Fish and Wildlife (ODFW; Report A), Washington Department of Fish and Wildlife (WDFW; Report B), U.S. Geological Survey Biological Resources Division (USGS; Report C), Columbia River Inter-Tribal Fish Commission (CRITFC; Report D), the U.S. Fish and Wildlife Service (USFWS; Report E), and Oregon State University (OSU; Report F). This is a multi-year study with many objectives requiring more than one year to complete; therefore, findings from a given year may be part of more significant findings yet to be reported. Highlights of results of our work from April 2000 through March 2001 are listed.

The authors report on their progress from April 1998 through March 1999 on determining the effects of mitigative measures on productivity of white sturgeon populations in the Columbia River downstream from McNary Dam, and on determining the status and habitat requirements of white sturgeon populations in the Columbia and Snake rivers upstream from McNary Dam. The study is a cooperative effort by the Oregon Department of Fish and Wildlife (ODFW; Report A), Washington Department of Fish and Wildlife (WDFW; Report B), U.S. Geological Survey Biological Resources Division (USGS; Report C), U.S. Fish and Wildlife Service (USFWS; Report D), Columbia River Inter-Tribal Fish Commission (CRITFC; Report E), and the University of Idaho (UI; Report F). This is a multi-year study with many objectives requiring more than one year to complete. Therefore, findings from a given year may be part of more significant findings yet to be reported. Highlights of results of our work from April 1998 through March 1999 are given.

We report on our progress from April 1999 through March 2000 on determining the effects of mitigative measures on productivity of white sturgeon populations in the Columbia River downstream from McNary Dam, and on determining the status and habitat requirements of white sturgeon populations in the Columbia and Snake rivers upstream from McNary Dam. The study is a cooperative effort by the Oregon Department of Fish and Wildlife (ODFW; Report A), Washington Department of Fish and Wildlife (WDFW; Report B), U.S. Geological Survey Biological Resources Division (USGS; Report C), Columbia River Inter-Tribal Fish Commission (CRITFC; Report D), and the U.S. Fish and Wildlife Service (USFWS; Report E). This is a multi-year study with many objectives requiring more than one year to complete. Therefore, findings from a given year may be part of more significant findings yet to be reported. Highlights of results of our work from April 1999 through March 2000 are given.

Discharges higher than are typically released from Alamo Dam in west-central Arizona were planned and released in 2005, 2006, 2007, 2008 and 2010 to study the effects of these releases on the Bill Williams River. The Bill Williams River Wildlife Refuge is located above the mouth of the Bill Williams River on Lake Havasu, and the river is the subject of ongoing ecological studies. Sediment concentrations and water discharges were measured in the Bill Williams River and turbidity, water temperature, specific conductance, pH, dissolved oxygen, and Secchi depth were measured in Lake Havasu during and after experimental releases in 2005 and 2006 from Alamo Dam. Additional measurements of the same parameters in the Bill Williams River and Lake Havasu were made during releases in 2010, and these are the subject of this report.

Chum (Oncorhynchus keta) and fall Chinook (O. tshawytscha) salmon segregate spatially during spawning in the Ives Island side channel of the lower Columbia River downstream from Bonneville Dam. Previous research during one spawning season (2000) suggested that these species selected spawning habitats based on differences in hyporheic temperature and vertical hydraulic gradient (VHG) with the river. In this study, we confirmed the spatial segregation of spawning based on hyporheic characteristics over four years (2001–2004) and examined the effects of load-following operations (power generation to meet short-term electrical demand) at Bonneville Dam on hyporheic function and characteristics. We found that during the study period, hyporheic temperature and VHG in chum salmon spawning areas were highly variable during periods of load-following operation when river levels fluctuated. In contrast, hyporheic water temperature and VHG within chum spawning areas fluctuated less when river levels were not changing due to load-following operation. Variable temperature and VHG could affect chum and fall Chinook salmon spawning segregation and incubation success by altering the cues each species uses to select redd sites. Alterations in site selection would result in a breakdown in the spatial segregation of spawning between chum and fall Chinook salmon, which would expose earlier spawning fall Chinook eggs to a greater risk of dislodgement from later spawning chum salmon. Additional research will be required to fully assess the effects of load-following operations on the hyporheic environment and spawning and incubation success of chum and fall Chinook salmon downstream from Bonneville Dam.

Since the production of nuclear material at SRS for weapons required large quantities of cooling water, a series of canals, dikes, and dams were constructed to provide conveyance systems and reservoirs. This paper presents a brief overview of the history of the construction of the dams and dikes. Attention is given to the use of asphaltic concrete for 30 years (and its maintenance and repair) to line the banks of dikes and the upstream slopes of dams to prevent erosion and possible failure. The ability of asphaltic concrete in preventing dam/dike failure was proven. Benefits and drawbacks to the use of this material are discussed based on the extensive experience at SRS.

Dam construction, flow diversion, and legacy landuse effects reduced the transport capacity, sediment supply, channel complexity and floodplain-connectivity along the Trinity River, CA below Lewiston Dam. This study documents the geomorphic evolution of the Trinity River Restoration Program’s intensively managed 65-km long restoration reach from 1980 to 2011. The nature and extent of riparian and channel changes were assessed using a series of geomorphic feature maps constructed from ortho-rectified photography acquired at low flow conditions in 1980, 1997, 2001, 2006, 2009, and 2011. Since 1980 there has been a general conversion of riparian to channel features and expansion of the active channel area. The primary mechanism for expansion of the active channel was bank erosion from 1980 to 1997 and channel widening was well distributed longitudinally throughout the study reach. Subsequent net bar accretion from 1997 to 2001, followed by slightly higher net bar scour from 2001 to 2006, occurred primarily in the central and lower reaches of the study area. In comparison, post-2006 bank and bar changes were spatially-limited to reaches with sufficient local transport capacity or sediment supply supported by gravel augmentation, mechanical channel rehabilitation, and tributary contributions to flow and sediment supply. A series of tributary floods in 1997, 1998 and 2006 were the primary factors leading to documented increases in channel complexity and floodplain connectivity. During the post-2006 period managed flow releases, in the absence of large magnitude tributary flooding, combined with gravel augmentation and mechanical restoration caused localized increases in sediment supply and transport capacity leading to smaller but measurable increases in channel complexity and floodplain connectivity primarily in the upper river below Lewiston Dam.

The Chijiawan creek, located in the mountains of Central Taiwan with a strongly seasonal hydrology, high discharge and sediment yields, is the only habitat in Taiwan of the endangered Formosan landlocked salmon. The 13-m-high No. 1 Check Dam was the largest and lowermost barrier on Chijiawan creek built in 1972. After forty years, the dam had 4-m scouring holes below its foundation, raising a significant risk of dam failure. Due to the safety concern and habitat restoration, the Shei-Pa National Park removed the dam in late May 2011. This paper documents the channel evolution after its removal by focusing on understanding the geomorphic responses to sediment processes and complexities of hydrological processes. We collected the hourly discharge data of a Taipower gaging station located 6.8 km from the dam from 2010 to 2013 and conducted surveys of grain size distributions, cross-sectional and longitudinal profiles, and carried out repeat photography. One month after dam removal, a one-year event (Typhoon Meari) excavated a wedge of sediment from the impoundment. The knickpoint migrated to 200 m upstream from the dam and about 20,000 m3 of sediment had eroded from the reservoir. The profile remained pretty much unchanged until a year after in June 2012. Following a 20-year event (Typhoon Saola) in August 2012, the highest flow after dam removal to present, the channel significantly changed and the knickpoint migrated to 800 m upstream to the dam. The cumulative eroded amount increased to 150,000 m3, about three-thirds of the former impounded sediment. After a 5-year event (Typhoon Soulik) later on in July 2013, the knickpoint did not show much difference and the eroded amount of impounded sediment only increased 10,000 m3. However, the surveyed cross-sections showed obvious channel form changes and thalweg migration. It is likely that the entire bed was mobilized during the earlier high flows (Typhoon Saola), resulting in more easily mobilized bed material. As many

The formation of lahars and a debris avalanche during Holocene eruptions of the Spurr volcanic complex in south-central Alaska have led to the development of volcanic debris dams in the Chakachatna River valley. Debris dams composed of lahar and debris-avalanche deposits formed at least five times in the last 8000-10,000 years and most recently during eruptions of Crater Peak vent in 1953 and 1992. Water impounded by a large debris avalanche of early Holocene (?) age may have destabilized an upstream glacier-dammed lake causing a catastrophic flood on the Chakachatna River. A large alluvial fan just downstream of the debris-avalanche deposit is strewn with boulders and blocks and is probably the deposit generated by this flood. Application of a physically based dam-break model yields estimates of peak discharge (Qp) attained during failure of the debris-avalanche dam in the range 104 < Qp < 106 m3 s-1 for plausible breach erosion rates of 10-100 m h-1. Smaller, short-lived, lahar dams that formed during historical eruptions in 1953, and 1992, impounded smaller lakes in the upper Chakachatna River valley and peak flows attained during failure of these volcanic debris dams were in the range 103 < Qp < 104 m3 s-1 for plausible breach erosion rates. Volcanic debris dams have formed at other volcanoes in the Cook Inlet region, Aleutian arc, and Wrangell Mountains but apparently did not fail rapidly or result in large or catastrophic outflows. Steep valley topography and frequent eruptions at volcanoes in this region make for significant hazards associated with the formation and failure of volcanic debris dams. Published by Elsevier Science B.V.

We analyzed five years of route-specific fish-passage data acquired by fixed-aspect hydroacoustic sampling of juvenile salmonids passing downstream through Bonneville Dam. High passage effectiveness of surface-flow outlets relative to the spillway and turbines suggests that juvenile salmonids are preferentially selecting surface outlets over adjacent turbines. Seasonal estimates showed that median combined effectiveness of surface-flow outlets (7.8) was 7.1 times higher than that of the spillway (1.1) and 9.8 times higher than that of turbines (0.8). Islands prevent the spillway from attracting fish from either powerhouse, something that may occur at other projects. Regressions indicated that percent flow passing a specific route explained from 50 to 97% of fish-passage variation, and relations were useful for evaluating fish-passage alternatives. Fitted curves for surface-passage routes, including the sluiceway at Powerhouse 1 (B1) and Powerhouse 2 (B2) were much steeper at low percent low (2-15%) than were curves for the spillway or turbines. Regressions indicate that increasing surface-flow percentages of B1 flow from 1% to 10% could increase B1 sluiceway-passage efficiency from 40% to 83%. Increasing B2 flow to the B2 sluiceway from 4% to 15% could increase fish passage from 31% to 62%. Without spill, about 50% of fish passed by non-turbine routes.

The Department of Energy (DOE) has prepared an environmental assessment (EA) (DOE/EA-1285) for the proposed repair of the Pond B dam at the Savannah River Site (SRS), located near Aiken, South Carolina. Based on the analyses in the EA, DOE has determined that the proposed action is not a major Federal action significantly affecting the quality of the human environment within the meaning of the National Environmental Policy Act of 1969 (NEPA). Therefore, the preparation of an environmental impact statement (EIS) is not required, and DOE is issuing this Finding of No Significant Impact (FONSI) and Floodplain Statement of Findings.

The U.S. Geological Survey collected hydrologic data at 12 continuous-record stations along the Colorado River and its major tributaries between Glen Canyon Dam and Diamond Creek. The data were collected from October 1989 through September 1995 as part of the Bureau of Reclamation's Glen Canyon Environmental Studies. The data include daily values for streamflow discharge, suspended-sediment discharge, temperature, specific conductance, pH, and dissolved-oxygen concentrations, and discrete values for physical properties and chemical constituents of water. All data are presented in tabular form.

This report provides reach survival and travel time estimates for PIT-tagged hatchery and wild juvenile steelhead and yearling chinook salmon in the Snake and Columbia Rivers during 1998. Estimates of post-detection bypass survival for yearling chinook salmon at McNary Dam are also reported. Results are reported primarily in the form of data tables and figures with minimal description of methods and analysis. Detailed information on the methodology and statistical models used for this report is provided in five previous annual reports on this study, which are cited here.

Floods increase fluvial complexity by eroding established surfaces and creating new alluvial surfaces. As dams regulate channel flow, fluvial complexity often decreases and the hydro-eco-geomorphology of the riparian habitat changes. Along the Missouri River, flow regulation resulted in channel incision of 1-3 m within the study area and disconnected the pre-dam floodplain from the channel. Evidence of fluvial complexity along the pre-dam Missouri River floodplain can be observed through the diverse depositional environments represented by areas of varying soil texture. This study evaluates the role of flow regulation and depositional environment along the Missouri River in the riparian invasion of red cedar downstream of Gavins Point dam, the final dam on the Missouri River. We determine whether invasion began before or after flow regulation, determine patterns of invasion using Bayesian t-tests, and construct a Bayesian multivariate linear model of invaded surfaces. We surveyed 59 plots from 14 riparian cottonwood stands for tree age, plot composition, plot stem density, and soil texture. Red cedars existed along the floodplain prior to regulation, but at a much lower density than today. We found 2 out of 565 red cedars established prior to regulation. Our interpretation of depositional environments shows that the coarser, sandy soils reflect higher energy depositional pre-dam surfaces that were geomorphically active islands and point bars prior to flow regulation and channel incision. The finer, clayey soils represent lower energy depositional pre-dam surfaces, such as swales or oxbow depressions. When determining patterns of invasion for use in a predictive statistical model, we found that red cedar primarily establishes on the higher energy depositional pre-dam surfaces. In addition, as cottonwood age and density decrease, red cedar density tends to increase. Our findings indicate that flow regulation caused hydrogeomorphic changes within the study area that

In June 2006, an opportunistic high-flow release was made from Tiber Dam on the Marias River in Montana to investigate possible alternatives for partially restoring the river's natural flow pattern and variability. At two sites along the river, we measured channel geometry in 2006 before and after the high-flow release to evaluate channel change and alteration of physical habitat. Here we provide data from a resurvey of those sites, conducted in August 2007.

Morris Sheppard Dam is one of the world`s largest flat slab buttress dams. It is located on the Brazos River about 96 km (60 miles) west of Dallas - Fort Worth. Designed by Ambursen Dam Company, the dam was constructed between 1938 and 1941 at a cost of $8.7 million. In 1987, a maximum buttress movement of 114 mm (4.5 inches) was discovered. The dam was successfully rehabilitated between 1987 and 1994 at a cost of $36 million. This paper will describe: (1) the dam`s construction and operational history, (2) the lowering of the reservoir by 3.94 m (13 feet) as an emergency response when the movement was discovered, (3) the initial stabilization of the dam by the addition of relief wells and grouting, (4) the final stabilization using ballast to increase the weight of the dam, (5) the use of actual dam performance as a full-scale, long-term, load test to back-calculate realistic strength parameters, (6) the multiple sets of design stability criteria used to analyze the structure, and (7) the use of model studies to enlarge the dam`s stilling basin and design an emergency spillway to handle the PMF.

The removal of two dams on the Elwha River will introduce massive volumes of sediment to the river, and this increase in sediment supply in the river will likely modify the shapes and forms of the river and coastal landscape downstream of the dams. This chapter provides the geologic and geomorphologic background of the Olympic Peninsula and the Elwha River with emphasis on the present river and shoreline. The Elwha River watershed was formed through the uplift of the Olympic Mountains, erosion and movement of sediment throughout the watershed from glaciers, and downslope movement of sediment from gravitational and hydrologic forces. Recent alterations to the river morphology and sediment movement through the river include the two large dams slated to be removed in 2011, but also include repeated bulldozing of channel boundaries, construction and maintenance of flood plain levees, a weir and diversion channel for water supply purposes, and engineered log jams to help enhance river habitat for salmon. The shoreline of the Elwha River delta has changed in location by several kilometers during the past 14,000 years, in response to variations in the local sea-level of approximately 150 meters. Erosion of the shoreline has accelerated during the past 80 years, resulting in landward movement of the beach by more than 200 meters near the river mouth, net reduction in the area of coastal wetlands, and the development of an armored low-tide terrace of the beach consisting primarily of cobble. Changes to the river and coastal morphology during and following dam removal may be substantial, and consistent, long-term monitoring of these systems will be needed to characterize the effects of the dam removal project.

Flaming Gorge Dam, a hydroelectric facility operated by the Bureau of Reclamation (Reclamation), is located on the Green River in Daggett County, northeastern Utah. Until recently, and since the early 1990s, single daily peak releases or steady flows have been the operational pattern of the dam during the winter period. However, releases from Flaming Gorge Reservoir followed a double-peak pattern (two daily flow peaks) during the winters of 2006-2007 and 2008-2009. Because there is little recent long-term history of double-peaking at Flaming Gorge Dam, the potential effects of double-peaking operations on trout body condition in the dam's tailwater are not known. A study plan was developed that identified research activities to evaluate potential effects from winter double-peaking operations (Hayse et al. 2009). Along with other tasks, the study plan identified the need to conduct a statistical analysis of historical trout condition and macroinvertebrate abundance to evaluate the potential effects of hydropower operations. The results from analyses based on the combined size classes of trout (85-630 mm) were presented in Magnusson et al. (2008). The results of this earlier analysis suggested possible relationships between trout condition and flow, but concern that some of the relationships resulted from size-based effects (e.g., apparent changes in condition may have been related to concomitant changes in size distribution, because small trout may have responded differently to flow than large trout) prompted additional analysis of within-size class relationships. This report presents the results of analyses of three different size classes of trout (small: 200-299 mm, medium: 300-399 mm, and large: {ge}400 mm body length). We analyzed historical data to (1) describe temporal patterns and relationships among flows, benthic macroinvertebrate abundance, and condition of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) in the tailwaters of Flaming

The effect of unsteadiness or dam releases on velocity and longitudinal dispersion of flow was evaluated by injecting a fluorescent dye into the Colorado River below Glen Canyon Dam and sampling for dye concentration at selected sites downstream. In Glen Canyon, average flow velocity through the study reach increased directly with discharge, but dispersion was greatest at the lowest of the three flows measured. In Grand Canyon, average flow velocity varied slightly from subreach to subreach at both steady and unsteady flow over the entire study reach. Also, longitudinal dispersion was not significantly different during steady and unsteady flow. Absence of tails on the curves shows that, at the measured flows, the eddies that are characteristic of the Grand Canyon reach do not trap water for a significant length of time. Data from the measurements were used to calibrate a one-dimensional now modeland a solute-transport model. The combined set of calibrated flow and solute-transport models was then used to predict velocity and dispersion at potential dam-release patterns.

Low-head dams in arid regions restrict fish movement and create novel habitats that have complex effects on fish assemblages. The influence of low-head dams and artificial wetlands on fishes in Muddy Creek, a tributary of the Colorado River system in the USA was examined. Upstream, fish assemblages were dominated by native species including two species of conservation concern, bluehead sucker, Catostomus discobolus Cope, and roundtail chub, Gila robusta Baird and Girard. The artificial wetlands contained almost exclusively non-native fathead minnow, Pimephales promelas Rafinesque, and white sucker, Catostomus commersonii (Lacep??de). Downstream, fish assemblages were dominated by non-native species. Upstream spawning migrations by non-native white suckers were blocked by dams associated with the wetlands. However, the wetlands do not provide habitat for native fishes and likely inhibit fish movement. The wetlands appear to be a source habitat for non-native fishes and a sink habitat for native fishes. Two non-native species, sand shiner, Notropis stramineus (Cope), and redside shiner, Richardsonius balteatus (Richardson), were present only downstream of the wetlands, suggesting a beneficial role of the wetlands in preventing upstream colonisation by non-native fishes. ?? 2009 Blackwell Publishing Ltd.

Peaking hydropower operations can profoundly alter natural stream flow and thereby affect the natural resources dependent on these flows. In this paper, we describe how aerial videography was used to collect environmental data and evaluate impacts of hydropower operations at Flaming Gorge Dam on natural resources of the Green River. An airborne multispectral video/radiometer remote sensing system was used to collect resource data under four different flow conditions from seven sites (each about one mile in length) located downstream from the dam. Releases from Flaming Gorge Dam during data collection ranged from approximately 800 to 4,000 cubic feet/sec (cfs), spanning most of the normal operating range for this facility. For each site a series of contiguous, non-overlapping images was prepared from the videotapes and used to quantify surface water area, backwater habitats, and areas of riparian vegetation under varying flow conditions. From this information, relationships between flow and habitat parameters were developed and used in conjunction with hydrologic modeling and ecological information to evaluate impacts of various modes of operation.

Dynamiting a hole at the base of the 38-m-high Condit Dam, on the White Salmon River, Washington, resulted in rapid reservoir drainage and erosion and produced a downstream surge of water and sediment. To document the short-term upstream and downstream responses to the October 2011 Condit breach, we combined photographic methods, topographic surveys, stage and suspended sediment measurements, and stratigraphic observations. Initial reservoir erosion occurred as a result of mass failure of thick, fine-grained reservoir sediment, which was eventually supplemented by knickpoint migration as the erosion propagated upstream from the dam. About 10 percent of total reservoir sediment eroded in the first 90 minutes after the breach, and about one-third of the reservoir sediment had evacuated in the first week. Downstream, an initially sediment-poor discharge peak with an approximately 100-year recurrence interval was followed by a hyperconcentrated sediment pulse (32% by volume) that locally produced meters-thick sand deposits. The post-breach sediment dynamics at Condit were in many respects more analogous to sediment pulses introduced by volcanic eruptions or large mass failure events than by previous dam removals.

In recent years, with increased effort to bypass and guide fragile stocks of juvenile salmon in the Columbia Basin past hydroelectric projects, it has been increasingly important to obtain fine-scale fish behavior data in a non-intrusive manner. The Dual-Head Multibeam Sonar is an emerging technology for fisheries applications that addresses that requirement. It has two principal advantages over traditional hydroacoustic techniques: (1) it allows for simultaneous large-volume coverage of a region of interest, and (2) it affords 3-D tracking capability. The use of Dual-Head Multibeam Sonar in this study resulted in unprecedented insight into fine-scale smolt behavior upstream of a prototype surface collector at Bonneville Dam first powerhouse in 1998. Our results indicated that outmigrant juvenile salmon had an increased likelihood of milling or holding. This discovery will lead to better design criteria for future bypass and collector systems. Future fisheries multibeam sonar systems will likely be fully integrated systems with built-in real time tracking capability. These systems may be used to track targets relative to physical guidance structures or other behavior modifying stimuli such as light, turbulent flow, electrical/magnetic fields, or low-frequency sound and vibration. The combination of fine-scale fish behavior data and environmental parameters will yield better design criteria for the safe passage of listed or endangered species of Pacific salmon.

An interdisciplinary study was carried out in order to trace the human transformation of the medium-scale Havel River in northeastern central Europe during the last c. 2000 years. This research was driven by the hypothesis that the present-day riverscape is widely a legacy of medieval and modern human transformation of the drainage system initiated essentially by damming for the operation of water mills. Recent opportunities to investigate the extent of this human impact arose during the course of archaeological rescue excavations and palaeoecologic studies, which significantly enhanced the amount of respective high-quality data. Along the middle course of the Havel, sedimentary sequences were analysed in order to explore the potential for reconstructing regional water-level dynamics. The river, draining the Berlin metropolitan area, forms a chain of dammed lakes and meandering river sections which were strongly modified by hydraulic engineering in the past. We have not only recorded new sections but also re-evaluated older ones, forming a total of sixteen sedimentary sequences along the river. Chronological control is provided by a multitude of palynological, dendrochronological, archaeological, and radiocarbon data. The sections upriver from the Brandenburg/H. and Spandau weirs, representing sites with historic water mills, reveal substantial water-level changes during the late Holocene. Generally, lower water levels before and higher levels parallel to the medieval German colonisation of that area (c. 1180/1250 AD) can be inferred. This water-level increase, which is attributed to be caused by medieval mill stowage, took place rapidly and amounted to a relative height of c. 1.5 m. It has caused the widening of river sections and the enlargement of existing lakes or its secondary formation when already aggraded, and thus a flooding of large portions of land. The rising water level has even influenced the settlement topography to a large degree. Several medieval

After damming the Colorado River the freshwater flow was reduced to 1% of its virgin flow to the Upper Gulf of California (UGC). The ecological effects need to be properly documented. The UGC is the nursery area for Litopenaeus stylirostris, the most profitable fishery in the zone. In order to know the relative abundance of L. stylirostris postlarval stage we conducted a sampled survey every 14 days in 1993, 1994 and 1997, plus an intensive sampling during a complete tide cycle in July 1995 and 1996. We did 10 min trawls each hour during the flood tide. Relative abundance of postlarvae was higher (p < 0.05) in those years when freshwater flow reached the UGC. PMID:11487932

New river discharge data are brought together with spacebased sea surface salinity measurements by Aquarius and SMOS to demonstrate the role of river discharge in salinity changes near three river mouths: the Mississippi, the Ganges, and the Amazon. The characteristics of the seasonal cycle and the year-to-year changes of the river runoff are described. Various versions of the satellite salinity data are compared. The relative roles of river discharge, surface water flux, and horizontal advection in changing surface salinity in regions near the river mouths are examined. Satellite measurements of SSS clearly track movements of the fresh water from river discharges. Besides the river discharge, E-P plays an important role in the seasonal salinity variation near the Ganges and Irrawaddy River mouths. For the Mississippi and Amazon river mouths, central and eastern ITCZ, E-P contributes very little to the salinity seasonal change. In the central and eastern ITCZ, contribution of advection to the salinity tendency is clearly identified. Both salinity and salinity tendency are dominated by semi-annual cycle in the Atlantic ITCZ between 5ºN to 9ºN, whereas annual cycle dominates at other latitudes.

Land and water resource development can independently eliminate riparian plant communities, including Fremont cottonwood forest (CF), a major contributor to ecosystem structure and functioning in semiarid portions of the American Southwest. We tested whether floodplain development was linked to river regulation in the Upper Colorado River Basin (UCRB) by relating the extent of five developed land-cover categories as well as CF and other natural vegetation to catchment reservoir capacity, changes in total annual and annual peak discharge, and overall level of mainstem hydrologic alteration (small, moderate, or large) in 26 fourth-order subbasins. We also asked whether CF appeared to be in jeopardy at a regional level. We classified 51% of the 57,000 ha of alluvial floodplain examined along >2600 km of mainstem rivers as CF and 36% as developed. The proportion developed was unrelated to the level of mainstem hydrologic alteration. The proportion classified as CF was also independent of the level of hydrologic alteration, a result we attribute to confounding effects from development, the presence of time lags, and contrasting effects from flow alteration in different subbasins. Most CF (68% by area) had a sparse canopy (???5% cover), and stands with >50% canopy cover occupied <1% of the floodplain in 15 subbasins. We suggest that CF extent in the UCRB will decline markedly in the future, when the old trees on floodplains now disconnected from the river die and large areas change from CF to non-CF categories. Attention at a basinwide scale to the multiple factors affecting cottonwood patch dynamics is needed to assure conservation of these riparian forests. ?? 2007 Springer Science+Business Media, LLC.

To understand the effects of increased sediment supply from dam removal on marine habitats around the Elwha River delta, a basic understanding of the region’s coastal processes is necessary. This chapter provides a summary of the physical setting of the coast near the Elwha River delta, for the purpose of synthesizing the processes that move and disperse sediment discharged by the river. One fundamental property of this coastal setting is the difference between currents in the surfzone with those in the coastal waters offshore of the surfzone. Surfzone currents are largely dictated by the direction and size of waves, and the waves that attack the Elwha River delta predominantly come from Pacific Ocean swell from the west. This establishes surfzone currents and littoral sediment transport that are eastward along much of the delta. Offshore of the surfzone the currents are largely influenced by tidal circulation and the physical constraint to flow provided by the delta’s headland. During both ebbing and flooding tides, the flow separates from the coast at the tip of the delta’s headland, and this produces eddies on the downstream side of the headland. Immediately offshore of the Elwha River mouth, this creates a situation in which the coastal currents are directed toward the east much more frequently than toward the west. This suggests that Elwha River sediment will be more likely to move toward the east in the coastal system.

Zebra mussel veliger densities were monitored throughout 1996 at Lock and Dam 52 on the lower Ohio River near Brookport, IL. The spawning season occurred between mid June and early September with veliger densities peaking at 30,000/m3 in late June. Veliger first appeared at a water temperature of 21° C. When